diff --git a/spec/compiler/semantic/class_spec.cr b/spec/compiler/semantic/class_spec.cr
index 88c3dd474a3f..2445a9eedf5f 100644
--- a/spec/compiler/semantic/class_spec.cr
+++ b/spec/compiler/semantic/class_spec.cr
@@ -383,6 +383,20 @@ describe "Semantic: class" do
       ") { char }
   end
 
+  it "type def does not reopen type from parent namespace (#11181)" do
+    assert_type <<-CR, inject_primitives: false { types["Baz"].types["Foo"].types["Bar"].metaclass }
+      class Foo::Bar
+      end
+
+      module Baz
+        class Foo::Bar
+        end
+      end
+
+      Baz::Foo::Bar
+      CR
+  end
+
   it "finds in global scope if includes module" do
     assert_type("
       class Baz
diff --git a/spec/compiler/semantic/module_spec.cr b/spec/compiler/semantic/module_spec.cr
index a55efaf93a3d..46de0bd0f4c0 100644
--- a/spec/compiler/semantic/module_spec.cr
+++ b/spec/compiler/semantic/module_spec.cr
@@ -898,6 +898,20 @@ describe "Semantic: module" do
       )) { types["Foo"].types["Bar"].types["Baz"].metaclass }
   end
 
+  it "type def does not reopen type from parent namespace (#11181)" do
+    assert_type <<-CR, inject_primitives: false { types["Baz"].types["Foo"].types["Bar"].metaclass }
+      module Foo::Bar
+      end
+
+      module Baz
+        module Foo::Bar
+        end
+      end
+
+      Baz::Foo::Bar
+      CR
+  end
+
   it "correctly types type var in included module, with a restriction with a free var (bug)" do
     assert_type(%(
       module Moo(T)
diff --git a/src/compiler/crystal/semantic/top_level_visitor.cr b/src/compiler/crystal/semantic/top_level_visitor.cr
index 98ceb23df6b3..1fc7119b9ffd 100644
--- a/src/compiler/crystal/semantic/top_level_visitor.cr
+++ b/src/compiler/crystal/semantic/top_level_visitor.cr
@@ -1275,7 +1275,7 @@ class Crystal::TopLevelVisitor < Crystal::SemanticVisitor
 
   def lookup_type_def_name_creating_modules(path : Path)
     base_type = path.global? ? program : current_type
-    target_type = base_type.lookup_path(path).as?(Type).try &.remove_alias_if_simple
+    target_type = base_type.lookup_path(path, lookup_in_namespace: false).as?(Type).try &.remove_alias_if_simple
 
     unless target_type
       next_type = base_type