diff --git a/CHANGELOG.md b/CHANGELOG.md
index 40a2d53690..7478aea5b5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -48,6 +48,11 @@
   [Martin Redington](https://github.com/mildm8nnered)
   [#5120](https://github.com/realm/SwiftLint/issues/5120)
 
+* Fix some unexpected rule enablement interactions between parent and
+  child configurations.  
+  [Martin Redington](https://github.com/mildm8nnered)
+  [#4876](https://github.com/realm/SwiftLint/issues/4876)
+
 ## 0.52.4: Lid Switch
 
 #### Breaking
diff --git a/Source/SwiftLintCore/Extensions/Configuration+RulesWrapper.swift b/Source/SwiftLintCore/Extensions/Configuration+RulesWrapper.swift
index 766ac3420d..6ae6fe5f3f 100644
--- a/Source/SwiftLintCore/Extensions/Configuration+RulesWrapper.swift
+++ b/Source/SwiftLintCore/Extensions/Configuration+RulesWrapper.swift
@@ -233,10 +233,7 @@ internal extension Configuration {
 
                 // Only use parent disabled / optIn if child config doesn't tell the opposite
                 return .default(
-                    disabled: Set(childDisabled).union(Set(disabled.filter { !childOptIn.contains($0) }))
-                        .filter {
-                            !isOptInRule($0, allRulesWrapped: newAllRulesWrapped)
-                        },
+                    disabled: Set(childDisabled).union(Set(disabled.filter { !childOptIn.contains($0) })),
                     optIn: Set(childOptIn).union(Set(optIn.filter { !childDisabled.contains($0) }))
                         .filter {
                             isOptInRule($0, allRulesWrapped: newAllRulesWrapped)
@@ -262,7 +259,7 @@ internal extension Configuration {
                 // Allow parent only rules that weren't disabled via the child config
                 // & opt-ins from the child config
                 return .only(Set(
-                    childOptIn + onlyRules.filter { !childDisabled.contains($0) }
+                    childOptIn.union(onlyRules).filter { !childDisabled.contains($0) }
                 ))
 
             case .allEnabled:
diff --git a/Tests/SwiftLintFrameworkTests/ConfigurationTests+MultipleConfigs.swift b/Tests/SwiftLintFrameworkTests/ConfigurationTests+MultipleConfigs.swift
index f6dc87dc18..67d4611214 100644
--- a/Tests/SwiftLintFrameworkTests/ConfigurationTests+MultipleConfigs.swift
+++ b/Tests/SwiftLintFrameworkTests/ConfigurationTests+MultipleConfigs.swift
@@ -301,6 +301,122 @@ extension ConfigurationTests {
         )
     }
 
+    func testParentChildOptInAndDisable() {
+        struct TestCase: Equatable {
+            let optedInInParent: Bool
+            let disabledInParent: Bool
+            let optedInInChild: Bool
+            let disabledInChild: Bool
+            let isEnabled: Bool
+            var message: String {
+                "optedInInParent = \(optedInInParent) " +
+                "disabledInParent = \(disabledInParent) " +
+                "optedInInChild = \(optedInInChild) " +
+                "disabledInChild = \(disabledInChild)"
+            }
+        }
+        let testCases: [TestCase] = [
+            // swiftlint:disable line_length
+            TestCase(optedInInParent: false, disabledInParent: false, optedInInChild: false, disabledInChild: false, isEnabled: false),
+            TestCase(optedInInParent: true, disabledInParent: false, optedInInChild: false, disabledInChild: false, isEnabled: true),
+            TestCase(optedInInParent: false, disabledInParent: true, optedInInChild: false, disabledInChild: false, isEnabled: false),
+            TestCase(optedInInParent: true, disabledInParent: true, optedInInChild: false, disabledInChild: false, isEnabled: false),
+            TestCase(optedInInParent: false, disabledInParent: false, optedInInChild: true, disabledInChild: false, isEnabled: true),
+            TestCase(optedInInParent: true, disabledInParent: false, optedInInChild: true, disabledInChild: false, isEnabled: true),
+            TestCase(optedInInParent: false, disabledInParent: true, optedInInChild: true, disabledInChild: false, isEnabled: true),
+            TestCase(optedInInParent: true, disabledInParent: true, optedInInChild: true, disabledInChild: false, isEnabled: true),
+            TestCase(optedInInParent: false, disabledInParent: false, optedInInChild: false, disabledInChild: true, isEnabled: false),
+            TestCase(optedInInParent: true, disabledInParent: false, optedInInChild: false, disabledInChild: true, isEnabled: false),
+            TestCase(optedInInParent: false, disabledInParent: true, optedInInChild: false, disabledInChild: true, isEnabled: false),
+            TestCase(optedInInParent: true, disabledInParent: true, optedInInChild: false, disabledInChild: true, isEnabled: false),
+            TestCase(optedInInParent: false, disabledInParent: false, optedInInChild: true, disabledInChild: true, isEnabled: false),
+            TestCase(optedInInParent: true, disabledInParent: false, optedInInChild: true, disabledInChild: true, isEnabled: false),
+            TestCase(optedInInParent: false, disabledInParent: true, optedInInChild: true, disabledInChild: true, isEnabled: false),
+            TestCase(optedInInParent: true, disabledInParent: true, optedInInChild: true, disabledInChild: true, isEnabled: false)
+            // swiftlint:enable line_length
+        ]
+        XCTAssertEqual(testCases.unique.count, 4 * 4)
+        let ruleType = ImplicitReturnRule.self
+        XCTAssertTrue((ruleType as Any) is OptInRule.Type)
+        let ruleIdentifier = ruleType.description.identifier
+        for testCase in testCases {
+            let parentConfiguration = Configuration(rulesMode: .default(
+                disabled: testCase.disabledInParent ? [ruleIdentifier] : [],
+                optIn: testCase.optedInInParent ? [ruleIdentifier] : []
+            ))
+            let childConfiguration = Configuration(rulesMode: .default(
+                disabled: testCase.disabledInChild ? [ruleIdentifier] : [],
+                optIn: testCase.optedInInChild ? [ruleIdentifier] : []
+            ))
+            let mergedConfiguration = parentConfiguration.merged(withChild: childConfiguration, rootDirectory: "")
+            let isEnabled = mergedConfiguration.contains(rule: ruleType)
+            XCTAssertEqual(isEnabled, testCase.isEnabled, testCase.message)
+        }
+    }
+
+    func testParentChildDisableForDefaultRule() {
+        struct TestCase: Equatable {
+            let disabledInParent: Bool
+            let disabledInChild: Bool
+            let isEnabled: Bool
+            var message: String {
+                "disabledInParent = \(disabledInParent) disabledInChild = \(disabledInChild)"
+            }
+        }
+        let testCases: [TestCase] = [
+            TestCase(disabledInParent: false, disabledInChild: false, isEnabled: true),
+            TestCase(disabledInParent: true, disabledInChild: false, isEnabled: false),
+            TestCase(disabledInParent: false, disabledInChild: true, isEnabled: false),
+            TestCase(disabledInParent: true, disabledInChild: true, isEnabled: false)
+        ]
+        XCTAssertEqual(testCases.unique.count, 2 * 2)
+        let ruleType = BlanketDisableCommandRule.self
+        XCTAssertFalse(ruleType is OptInRule.Type)
+        let ruleIdentifier = ruleType.description.identifier
+        for testCase in testCases {
+            let parentConfiguration = Configuration(
+                rulesMode: .default(disabled: testCase.disabledInParent ? [ruleIdentifier] : [], optIn: [])
+            )
+            let childConfiguration = Configuration(
+                rulesMode: .default(disabled: testCase.disabledInChild ? [ruleIdentifier] : [], optIn: [])
+            )
+            let mergedConfiguration = parentConfiguration.merged(withChild: childConfiguration, rootDirectory: "")
+            let isEnabled = mergedConfiguration.contains(rule: ruleType)
+            XCTAssertEqual(isEnabled, testCase.isEnabled, testCase.message)
+        }
+    }
+
+    func testParentOnlyRulesAndChildOptInAndDisabled() {
+        struct TestCase: Equatable {
+            let optedInInChild: Bool
+            let disabledInChild: Bool
+            let isEnabled: Bool
+            var message: String {
+                "optedInInChild = \(optedInInChild) disabledInChild = \(disabledInChild)"
+            }
+        }
+        let testCases: [TestCase] = [
+            TestCase(optedInInChild: false, disabledInChild: false, isEnabled: true),
+            TestCase(optedInInChild: true, disabledInChild: false, isEnabled: true),
+            TestCase(optedInInChild: false, disabledInChild: true, isEnabled: false),
+            TestCase(optedInInChild: true, disabledInChild: true, isEnabled: false)
+        ]
+        XCTAssertEqual(testCases.unique.count, 2 * 2)
+        let ruleType = ImplicitReturnRule.self
+        XCTAssertTrue((ruleType as Any) is OptInRule.Type)
+        let ruleIdentifier = ruleType.description.identifier
+        let parentConfiguration = Configuration(rulesMode: .only([ruleIdentifier]))
+        for testCase in testCases {
+            let childConfiguration = Configuration(rulesMode: .default(
+                disabled: testCase.disabledInChild ? [ruleIdentifier] : [],
+                optIn: testCase.optedInInChild ? [ruleIdentifier] : []
+            ))
+            let mergedConfiguration = parentConfiguration.merged(withChild: childConfiguration, rootDirectory: "")
+            let isEnabled = mergedConfiguration.contains(rule: ruleType)
+            XCTAssertEqual(isEnabled, testCase.isEnabled, testCase.message)
+        }
+    }
+
     // MARK: - Remote Configs
     func testValidRemoteChildConfig() {
         FileManager.default.changeCurrentDirectoryPath(Mock.Dir.remoteConfigChild)
diff --git a/Tests/SwiftLintFrameworkTests/Resources/ProjectMock/ChildConfig/Test2/expected.yml b/Tests/SwiftLintFrameworkTests/Resources/ProjectMock/ChildConfig/Test2/expected.yml
index 4e5c3fc58f..1f2108866c 100644
--- a/Tests/SwiftLintFrameworkTests/Resources/ProjectMock/ChildConfig/Test2/expected.yml
+++ b/Tests/SwiftLintFrameworkTests/Resources/ProjectMock/ChildConfig/Test2/expected.yml
@@ -2,7 +2,10 @@ opt_in_rules:
   - private_action
 
 disabled_rules:
+  - empty_count
   - force_cast
+  - private_outlet
+  - trailing_closure
 
 line_length: 80
 
diff --git a/Tests/SwiftLintFrameworkTests/Resources/ProjectMock/ParentConfig/Test2/expected.yml b/Tests/SwiftLintFrameworkTests/Resources/ProjectMock/ParentConfig/Test2/expected.yml
index 4e5c3fc58f..1f2108866c 100644
--- a/Tests/SwiftLintFrameworkTests/Resources/ProjectMock/ParentConfig/Test2/expected.yml
+++ b/Tests/SwiftLintFrameworkTests/Resources/ProjectMock/ParentConfig/Test2/expected.yml
@@ -2,7 +2,10 @@ opt_in_rules:
   - private_action
 
 disabled_rules:
+  - empty_count
   - force_cast
+  - private_outlet
+  - trailing_closure
 
 line_length: 80