diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 92a989a2bc707..09b9b57f41c3d 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -18759,7 +18759,9 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
     // An object type S is considered to be derived from an object type T if
     // S is a union type and every constituent of S is derived from T,
     // T is a union type and S is derived from at least one constituent of T, or
-    // S is a type variable with a base constraint that is derived from T,
+    // S is an intersection type and some constituent of S is derived from T, or
+    // S is a type variable with a base constraint that is derived from T, or
+    // T is {} and S is an object-like type (ensuring {} is less derived than Object), or
     // T is one of the global types Object and Function and S is a subtype of T, or
     // T occurs directly or indirectly in an 'extends' clause of S.
     // Note that this check ignores type parameters and only considers the
@@ -18767,8 +18769,10 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
     function isTypeDerivedFrom(source: Type, target: Type): boolean {
         return source.flags & TypeFlags.Union ? every((source as UnionType).types, t => isTypeDerivedFrom(t, target)) :
             target.flags & TypeFlags.Union ? some((target as UnionType).types, t => isTypeDerivedFrom(source, t)) :
+            source.flags & TypeFlags.Intersection ? some((source as IntersectionType).types, t => isTypeDerivedFrom(t, target)) :
             source.flags & TypeFlags.InstantiableNonPrimitive ? isTypeDerivedFrom(getBaseConstraintOfType(source) || unknownType, target) :
-            target === globalObjectType ? !!(source.flags & (TypeFlags.Object | TypeFlags.NonPrimitive)) :
+            isEmptyAnonymousObjectType(target) ? !!(source.flags & (TypeFlags.Object | TypeFlags.NonPrimitive)) :
+            target === globalObjectType ? !!(source.flags & (TypeFlags.Object | TypeFlags.NonPrimitive)) && !isEmptyAnonymousObjectType(source) :
             target === globalFunctionType ? !!(source.flags & TypeFlags.Object) && isFunctionObjectType(source as ObjectType) :
             hasBaseType(source, getTargetType(target)) || (isArrayType(target) && !isReadonlyArrayType(target) && isTypeDerivedFrom(source, globalReadonlyArrayType));
     }
diff --git a/tests/baselines/reference/inKeywordAndIntersection.js b/tests/baselines/reference/inKeywordAndIntersection.js
new file mode 100644
index 0000000000000..1fb275d24fc8e
--- /dev/null
+++ b/tests/baselines/reference/inKeywordAndIntersection.js
@@ -0,0 +1,59 @@
+//// [inKeywordAndIntersection.ts]
+class A { a = 0 }
+class B { b = 0 }
+
+function f10(obj: A & { x: string } | B) {
+    if (obj instanceof Object) {
+        obj;  // A & { x: string } | B
+    }
+    else {
+        obj;  // Error
+    }
+}
+
+// Repro from #50844
+
+interface InstanceOne {
+    one(): void
+}
+
+interface InstanceTwo {
+    two(): void
+}
+
+const instance = {} as InstanceOne | InstanceTwo
+
+const ClassOne = {} as { new(): InstanceOne } & { foo: true };
+
+if (instance instanceof ClassOne) {
+    instance.one();
+}
+
+
+//// [inKeywordAndIntersection.js]
+"use strict";
+var A = /** @class */ (function () {
+    function A() {
+        this.a = 0;
+    }
+    return A;
+}());
+var B = /** @class */ (function () {
+    function B() {
+        this.b = 0;
+    }
+    return B;
+}());
+function f10(obj) {
+    if (obj instanceof Object) {
+        obj; // A & { x: string } | B
+    }
+    else {
+        obj; // Error
+    }
+}
+var instance = {};
+var ClassOne = {};
+if (instance instanceof ClassOne) {
+    instance.one();
+}
diff --git a/tests/baselines/reference/inKeywordAndIntersection.symbols b/tests/baselines/reference/inKeywordAndIntersection.symbols
new file mode 100644
index 0000000000000..44e75202c87ec
--- /dev/null
+++ b/tests/baselines/reference/inKeywordAndIntersection.symbols
@@ -0,0 +1,65 @@
+=== tests/cases/compiler/inKeywordAndIntersection.ts ===
+class A { a = 0 }
+>A : Symbol(A, Decl(inKeywordAndIntersection.ts, 0, 0))
+>a : Symbol(A.a, Decl(inKeywordAndIntersection.ts, 0, 9))
+
+class B { b = 0 }
+>B : Symbol(B, Decl(inKeywordAndIntersection.ts, 0, 17))
+>b : Symbol(B.b, Decl(inKeywordAndIntersection.ts, 1, 9))
+
+function f10(obj: A & { x: string } | B) {
+>f10 : Symbol(f10, Decl(inKeywordAndIntersection.ts, 1, 17))
+>obj : Symbol(obj, Decl(inKeywordAndIntersection.ts, 3, 13))
+>A : Symbol(A, Decl(inKeywordAndIntersection.ts, 0, 0))
+>x : Symbol(x, Decl(inKeywordAndIntersection.ts, 3, 23))
+>B : Symbol(B, Decl(inKeywordAndIntersection.ts, 0, 17))
+
+    if (obj instanceof Object) {
+>obj : Symbol(obj, Decl(inKeywordAndIntersection.ts, 3, 13))
+>Object : Symbol(Object, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+
+        obj;  // A & { x: string } | B
+>obj : Symbol(obj, Decl(inKeywordAndIntersection.ts, 3, 13))
+    }
+    else {
+        obj;  // Error
+>obj : Symbol(obj, Decl(inKeywordAndIntersection.ts, 3, 13))
+    }
+}
+
+// Repro from #50844
+
+interface InstanceOne {
+>InstanceOne : Symbol(InstanceOne, Decl(inKeywordAndIntersection.ts, 10, 1))
+
+    one(): void
+>one : Symbol(InstanceOne.one, Decl(inKeywordAndIntersection.ts, 14, 23))
+}
+
+interface InstanceTwo {
+>InstanceTwo : Symbol(InstanceTwo, Decl(inKeywordAndIntersection.ts, 16, 1))
+
+    two(): void
+>two : Symbol(InstanceTwo.two, Decl(inKeywordAndIntersection.ts, 18, 23))
+}
+
+const instance = {} as InstanceOne | InstanceTwo
+>instance : Symbol(instance, Decl(inKeywordAndIntersection.ts, 22, 5))
+>InstanceOne : Symbol(InstanceOne, Decl(inKeywordAndIntersection.ts, 10, 1))
+>InstanceTwo : Symbol(InstanceTwo, Decl(inKeywordAndIntersection.ts, 16, 1))
+
+const ClassOne = {} as { new(): InstanceOne } & { foo: true };
+>ClassOne : Symbol(ClassOne, Decl(inKeywordAndIntersection.ts, 24, 5))
+>InstanceOne : Symbol(InstanceOne, Decl(inKeywordAndIntersection.ts, 10, 1))
+>foo : Symbol(foo, Decl(inKeywordAndIntersection.ts, 24, 49))
+
+if (instance instanceof ClassOne) {
+>instance : Symbol(instance, Decl(inKeywordAndIntersection.ts, 22, 5))
+>ClassOne : Symbol(ClassOne, Decl(inKeywordAndIntersection.ts, 24, 5))
+
+    instance.one();
+>instance.one : Symbol(InstanceOne.one, Decl(inKeywordAndIntersection.ts, 14, 23))
+>instance : Symbol(instance, Decl(inKeywordAndIntersection.ts, 22, 5))
+>one : Symbol(InstanceOne.one, Decl(inKeywordAndIntersection.ts, 14, 23))
+}
+
diff --git a/tests/baselines/reference/inKeywordAndIntersection.types b/tests/baselines/reference/inKeywordAndIntersection.types
new file mode 100644
index 0000000000000..7fc2b950501f7
--- /dev/null
+++ b/tests/baselines/reference/inKeywordAndIntersection.types
@@ -0,0 +1,66 @@
+=== tests/cases/compiler/inKeywordAndIntersection.ts ===
+class A { a = 0 }
+>A : A
+>a : number
+>0 : 0
+
+class B { b = 0 }
+>B : B
+>b : number
+>0 : 0
+
+function f10(obj: A & { x: string } | B) {
+>f10 : (obj: (A & {    x: string;}) | B) => void
+>obj : B | (A & { x: string; })
+>x : string
+
+    if (obj instanceof Object) {
+>obj instanceof Object : boolean
+>obj : B | (A & { x: string; })
+>Object : ObjectConstructor
+
+        obj;  // A & { x: string } | B
+>obj : B | (A & { x: string; })
+    }
+    else {
+        obj;  // Error
+>obj : never
+    }
+}
+
+// Repro from #50844
+
+interface InstanceOne {
+    one(): void
+>one : () => void
+}
+
+interface InstanceTwo {
+    two(): void
+>two : () => void
+}
+
+const instance = {} as InstanceOne | InstanceTwo
+>instance : InstanceOne | InstanceTwo
+>{} as InstanceOne | InstanceTwo : InstanceOne | InstanceTwo
+>{} : {}
+
+const ClassOne = {} as { new(): InstanceOne } & { foo: true };
+>ClassOne : (new () => InstanceOne) & { foo: true; }
+>{} as { new(): InstanceOne } & { foo: true } : (new () => InstanceOne) & { foo: true; }
+>{} : {}
+>foo : true
+>true : true
+
+if (instance instanceof ClassOne) {
+>instance instanceof ClassOne : boolean
+>instance : InstanceOne | InstanceTwo
+>ClassOne : (new () => InstanceOne) & { foo: true; }
+
+    instance.one();
+>instance.one() : void
+>instance.one : () => void
+>instance : InstanceOne
+>one : () => void
+}
+
diff --git a/tests/baselines/reference/inKeywordAndUnknown.errors.txt b/tests/baselines/reference/inKeywordAndUnknown.errors.txt
index 61c2cd2a2a364..59492364713ef 100644
--- a/tests/baselines/reference/inKeywordAndUnknown.errors.txt
+++ b/tests/baselines/reference/inKeywordAndUnknown.errors.txt
@@ -20,4 +20,38 @@ tests/cases/compiler/inKeywordAndUnknown.ts(12,18): error TS2638: Type '{}' may
         }
         y;  // {}
     }
+    
+    // Repro from #51007
+    
+    function isHTMLTable(table: unknown): boolean {
+        return !!table && table instanceof Object && 'html' in table;
+    }
+    
+    function f1(x: unknown) {
+        return x && x instanceof Object && 'a' in x;
+    }
+    
+    function f2<T>(x: T) {
+        return x && x instanceof Object && 'a' in x;
+    }
+    
+    function f3(x: {}) {
+        return x instanceof Object && 'a' in x;
+    }
+    
+    function f4<T extends {}>(x: T) {
+        return x instanceof Object && 'a' in x;
+    }
+    
+    function f5<T>(x: T & {}) {
+        return x instanceof Object && 'a' in x;
+    }
+    
+    function f6<T extends {}>(x: T & {}) {
+        return x instanceof Object && 'a' in x;
+    }
+    
+    function f7<T extends object>(x: T & {}) {
+        return x instanceof Object && 'a' in x;
+    }
     
\ No newline at end of file
diff --git a/tests/baselines/reference/inKeywordAndUnknown.js b/tests/baselines/reference/inKeywordAndUnknown.js
index 354bb8c4b1884..10b11c1b99c02 100644
--- a/tests/baselines/reference/inKeywordAndUnknown.js
+++ b/tests/baselines/reference/inKeywordAndUnknown.js
@@ -15,6 +15,40 @@ function f(x: {}, y: unknown) {
     }
     y;  // {}
 }
+
+// Repro from #51007
+
+function isHTMLTable(table: unknown): boolean {
+    return !!table && table instanceof Object && 'html' in table;
+}
+
+function f1(x: unknown) {
+    return x && x instanceof Object && 'a' in x;
+}
+
+function f2<T>(x: T) {
+    return x && x instanceof Object && 'a' in x;
+}
+
+function f3(x: {}) {
+    return x instanceof Object && 'a' in x;
+}
+
+function f4<T extends {}>(x: T) {
+    return x instanceof Object && 'a' in x;
+}
+
+function f5<T>(x: T & {}) {
+    return x instanceof Object && 'a' in x;
+}
+
+function f6<T extends {}>(x: T & {}) {
+    return x instanceof Object && 'a' in x;
+}
+
+function f7<T extends object>(x: T & {}) {
+    return x instanceof Object && 'a' in x;
+}
 
 
 //// [inKeywordAndUnknown.js]
@@ -34,3 +68,28 @@ function f(x, y) {
     }
     y; // {}
 }
+// Repro from #51007
+function isHTMLTable(table) {
+    return !!table && table instanceof Object && 'html' in table;
+}
+function f1(x) {
+    return x && x instanceof Object && 'a' in x;
+}
+function f2(x) {
+    return x && x instanceof Object && 'a' in x;
+}
+function f3(x) {
+    return x instanceof Object && 'a' in x;
+}
+function f4(x) {
+    return x instanceof Object && 'a' in x;
+}
+function f5(x) {
+    return x instanceof Object && 'a' in x;
+}
+function f6(x) {
+    return x instanceof Object && 'a' in x;
+}
+function f7(x) {
+    return x instanceof Object && 'a' in x;
+}
diff --git a/tests/baselines/reference/inKeywordAndUnknown.symbols b/tests/baselines/reference/inKeywordAndUnknown.symbols
index 145e92dc7f657..158c046b60044 100644
--- a/tests/baselines/reference/inKeywordAndUnknown.symbols
+++ b/tests/baselines/reference/inKeywordAndUnknown.symbols
@@ -31,3 +31,98 @@ function f(x: {}, y: unknown) {
 >y : Symbol(y, Decl(inKeywordAndUnknown.ts, 2, 17))
 }
 
+// Repro from #51007
+
+function isHTMLTable(table: unknown): boolean {
+>isHTMLTable : Symbol(isHTMLTable, Decl(inKeywordAndUnknown.ts, 15, 1))
+>table : Symbol(table, Decl(inKeywordAndUnknown.ts, 19, 21))
+
+    return !!table && table instanceof Object && 'html' in table;
+>table : Symbol(table, Decl(inKeywordAndUnknown.ts, 19, 21))
+>table : Symbol(table, Decl(inKeywordAndUnknown.ts, 19, 21))
+>Object : Symbol(Object, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>table : Symbol(table, Decl(inKeywordAndUnknown.ts, 19, 21))
+}
+
+function f1(x: unknown) {
+>f1 : Symbol(f1, Decl(inKeywordAndUnknown.ts, 21, 1))
+>x : Symbol(x, Decl(inKeywordAndUnknown.ts, 23, 12))
+
+    return x && x instanceof Object && 'a' in x;
+>x : Symbol(x, Decl(inKeywordAndUnknown.ts, 23, 12))
+>x : Symbol(x, Decl(inKeywordAndUnknown.ts, 23, 12))
+>Object : Symbol(Object, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>x : Symbol(x, Decl(inKeywordAndUnknown.ts, 23, 12))
+}
+
+function f2<T>(x: T) {
+>f2 : Symbol(f2, Decl(inKeywordAndUnknown.ts, 25, 1))
+>T : Symbol(T, Decl(inKeywordAndUnknown.ts, 27, 12))
+>x : Symbol(x, Decl(inKeywordAndUnknown.ts, 27, 15))
+>T : Symbol(T, Decl(inKeywordAndUnknown.ts, 27, 12))
+
+    return x && x instanceof Object && 'a' in x;
+>x : Symbol(x, Decl(inKeywordAndUnknown.ts, 27, 15))
+>x : Symbol(x, Decl(inKeywordAndUnknown.ts, 27, 15))
+>Object : Symbol(Object, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>x : Symbol(x, Decl(inKeywordAndUnknown.ts, 27, 15))
+}
+
+function f3(x: {}) {
+>f3 : Symbol(f3, Decl(inKeywordAndUnknown.ts, 29, 1))
+>x : Symbol(x, Decl(inKeywordAndUnknown.ts, 31, 12))
+
+    return x instanceof Object && 'a' in x;
+>x : Symbol(x, Decl(inKeywordAndUnknown.ts, 31, 12))
+>Object : Symbol(Object, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>x : Symbol(x, Decl(inKeywordAndUnknown.ts, 31, 12))
+}
+
+function f4<T extends {}>(x: T) {
+>f4 : Symbol(f4, Decl(inKeywordAndUnknown.ts, 33, 1))
+>T : Symbol(T, Decl(inKeywordAndUnknown.ts, 35, 12))
+>x : Symbol(x, Decl(inKeywordAndUnknown.ts, 35, 26))
+>T : Symbol(T, Decl(inKeywordAndUnknown.ts, 35, 12))
+
+    return x instanceof Object && 'a' in x;
+>x : Symbol(x, Decl(inKeywordAndUnknown.ts, 35, 26))
+>Object : Symbol(Object, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>x : Symbol(x, Decl(inKeywordAndUnknown.ts, 35, 26))
+}
+
+function f5<T>(x: T & {}) {
+>f5 : Symbol(f5, Decl(inKeywordAndUnknown.ts, 37, 1))
+>T : Symbol(T, Decl(inKeywordAndUnknown.ts, 39, 12))
+>x : Symbol(x, Decl(inKeywordAndUnknown.ts, 39, 15))
+>T : Symbol(T, Decl(inKeywordAndUnknown.ts, 39, 12))
+
+    return x instanceof Object && 'a' in x;
+>x : Symbol(x, Decl(inKeywordAndUnknown.ts, 39, 15))
+>Object : Symbol(Object, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>x : Symbol(x, Decl(inKeywordAndUnknown.ts, 39, 15))
+}
+
+function f6<T extends {}>(x: T & {}) {
+>f6 : Symbol(f6, Decl(inKeywordAndUnknown.ts, 41, 1))
+>T : Symbol(T, Decl(inKeywordAndUnknown.ts, 43, 12))
+>x : Symbol(x, Decl(inKeywordAndUnknown.ts, 43, 26))
+>T : Symbol(T, Decl(inKeywordAndUnknown.ts, 43, 12))
+
+    return x instanceof Object && 'a' in x;
+>x : Symbol(x, Decl(inKeywordAndUnknown.ts, 43, 26))
+>Object : Symbol(Object, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>x : Symbol(x, Decl(inKeywordAndUnknown.ts, 43, 26))
+}
+
+function f7<T extends object>(x: T & {}) {
+>f7 : Symbol(f7, Decl(inKeywordAndUnknown.ts, 45, 1))
+>T : Symbol(T, Decl(inKeywordAndUnknown.ts, 47, 12))
+>x : Symbol(x, Decl(inKeywordAndUnknown.ts, 47, 30))
+>T : Symbol(T, Decl(inKeywordAndUnknown.ts, 47, 12))
+
+    return x instanceof Object && 'a' in x;
+>x : Symbol(x, Decl(inKeywordAndUnknown.ts, 47, 30))
+>Object : Symbol(Object, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>x : Symbol(x, Decl(inKeywordAndUnknown.ts, 47, 30))
+}
+
diff --git a/tests/baselines/reference/inKeywordAndUnknown.types b/tests/baselines/reference/inKeywordAndUnknown.types
index 59a587598b23d..359651a5dec24 100644
--- a/tests/baselines/reference/inKeywordAndUnknown.types
+++ b/tests/baselines/reference/inKeywordAndUnknown.types
@@ -40,3 +40,125 @@ function f(x: {}, y: unknown) {
 >y : Record<"a", unknown>
 }
 
+// Repro from #51007
+
+function isHTMLTable(table: unknown): boolean {
+>isHTMLTable : (table: unknown) => boolean
+>table : unknown
+
+    return !!table && table instanceof Object && 'html' in table;
+>!!table && table instanceof Object && 'html' in table : boolean
+>!!table && table instanceof Object : boolean
+>!!table : boolean
+>!table : boolean
+>table : unknown
+>table instanceof Object : boolean
+>table : {}
+>Object : ObjectConstructor
+>'html' in table : boolean
+>'html' : "html"
+>table : Object
+}
+
+function f1(x: unknown) {
+>f1 : (x: unknown) => unknown
+>x : unknown
+
+    return x && x instanceof Object && 'a' in x;
+>x && x instanceof Object && 'a' in x : unknown
+>x && x instanceof Object : unknown
+>x : unknown
+>x instanceof Object : boolean
+>x : {}
+>Object : ObjectConstructor
+>'a' in x : boolean
+>'a' : "a"
+>x : Object
+}
+
+function f2<T>(x: T) {
+>f2 : <T>(x: T) => boolean
+>x : T
+
+    return x && x instanceof Object && 'a' in x;
+>x && x instanceof Object && 'a' in x : boolean
+>x && x instanceof Object : boolean
+>x : T
+>x instanceof Object : boolean
+>x : NonNullable<T>
+>Object : ObjectConstructor
+>'a' in x : boolean
+>'a' : "a"
+>x : T & Object
+}
+
+function f3(x: {}) {
+>f3 : (x: {}) => boolean
+>x : {}
+
+    return x instanceof Object && 'a' in x;
+>x instanceof Object && 'a' in x : boolean
+>x instanceof Object : boolean
+>x : {}
+>Object : ObjectConstructor
+>'a' in x : boolean
+>'a' : "a"
+>x : Object
+}
+
+function f4<T extends {}>(x: T) {
+>f4 : <T extends {}>(x: T) => boolean
+>x : T
+
+    return x instanceof Object && 'a' in x;
+>x instanceof Object && 'a' in x : boolean
+>x instanceof Object : boolean
+>x : T
+>Object : ObjectConstructor
+>'a' in x : boolean
+>'a' : "a"
+>x : T & Object
+}
+
+function f5<T>(x: T & {}) {
+>f5 : <T>(x: T & {}) => boolean
+>x : T & {}
+
+    return x instanceof Object && 'a' in x;
+>x instanceof Object && 'a' in x : boolean
+>x instanceof Object : boolean
+>x : T & {}
+>Object : ObjectConstructor
+>'a' in x : boolean
+>'a' : "a"
+>x : T & Object
+}
+
+function f6<T extends {}>(x: T & {}) {
+>f6 : <T extends {}>(x: T & {}) => boolean
+>x : T & {}
+
+    return x instanceof Object && 'a' in x;
+>x instanceof Object && 'a' in x : boolean
+>x instanceof Object : boolean
+>x : T & {}
+>Object : ObjectConstructor
+>'a' in x : boolean
+>'a' : "a"
+>x : T & Object
+}
+
+function f7<T extends object>(x: T & {}) {
+>f7 : <T extends object>(x: T & {}) => boolean
+>x : T & {}
+
+    return x instanceof Object && 'a' in x;
+>x instanceof Object && 'a' in x : boolean
+>x instanceof Object : boolean
+>x : T & {}
+>Object : ObjectConstructor
+>'a' in x : boolean
+>'a' : "a"
+>x : T & {}
+}
+
diff --git a/tests/cases/compiler/inKeywordAndIntersection.ts b/tests/cases/compiler/inKeywordAndIntersection.ts
new file mode 100644
index 0000000000000..dadf93a8649d0
--- /dev/null
+++ b/tests/cases/compiler/inKeywordAndIntersection.ts
@@ -0,0 +1,31 @@
+// @strict: true
+
+class A { a = 0 }
+class B { b = 0 }
+
+function f10(obj: A & { x: string } | B) {
+    if (obj instanceof Object) {
+        obj;  // A & { x: string } | B
+    }
+    else {
+        obj;  // Error
+    }
+}
+
+// Repro from #50844
+
+interface InstanceOne {
+    one(): void
+}
+
+interface InstanceTwo {
+    two(): void
+}
+
+const instance = {} as InstanceOne | InstanceTwo
+
+const ClassOne = {} as { new(): InstanceOne } & { foo: true };
+
+if (instance instanceof ClassOne) {
+    instance.one();
+}
diff --git a/tests/cases/compiler/inKeywordAndUnknown.ts b/tests/cases/compiler/inKeywordAndUnknown.ts
index 745dfbc1f9af5..4a43fa3932bbe 100644
--- a/tests/cases/compiler/inKeywordAndUnknown.ts
+++ b/tests/cases/compiler/inKeywordAndUnknown.ts
@@ -16,3 +16,37 @@ function f(x: {}, y: unknown) {
     }
     y;  // {}
 }
+
+// Repro from #51007
+
+function isHTMLTable(table: unknown): boolean {
+    return !!table && table instanceof Object && 'html' in table;
+}
+
+function f1(x: unknown) {
+    return x && x instanceof Object && 'a' in x;
+}
+
+function f2<T>(x: T) {
+    return x && x instanceof Object && 'a' in x;
+}
+
+function f3(x: {}) {
+    return x instanceof Object && 'a' in x;
+}
+
+function f4<T extends {}>(x: T) {
+    return x instanceof Object && 'a' in x;
+}
+
+function f5<T>(x: T & {}) {
+    return x instanceof Object && 'a' in x;
+}
+
+function f6<T extends {}>(x: T & {}) {
+    return x instanceof Object && 'a' in x;
+}
+
+function f7<T extends object>(x: T & {}) {
+    return x instanceof Object && 'a' in x;
+}