diff --git a/test/ClangImporter/Inputs/frameworks/CategoryOverrides.framework/Headers/CategoryOverrides.h b/test/ClangImporter/Inputs/frameworks/CategoryOverrides.framework/Headers/CategoryOverrides.h
index 03c13252ac497..4c66878d60f8a 100644
--- a/test/ClangImporter/Inputs/frameworks/CategoryOverrides.framework/Headers/CategoryOverrides.h
+++ b/test/ClangImporter/Inputs/frameworks/CategoryOverrides.framework/Headers/CategoryOverrides.h
@@ -19,3 +19,16 @@ typedef struct SomeStruct_s {
 @interface MyDerivedClass : MyBaseClass
 @property (nonatomic, strong, nullable) Base *derivedMember;
 @end
+
+typedef enum {
+  Caster,
+  Grantulated,
+  Confectioners,
+  Cane,
+  Demerara,
+  Turbinado,
+} RefinedSugar /*NS_REFINED_FOR_SWIFT*/ __attribute__((swift_private));
+
+@interface Refinery : Base
+@property (nonatomic, readonly) RefinedSugar sugar /*NS_REFINED_FOR_SWIFT*/ __attribute__((swift_private));
+@end
diff --git a/test/ClangImporter/Inputs/frameworks/CategoryOverrides.framework/PrivateHeaders/Private.h b/test/ClangImporter/Inputs/frameworks/CategoryOverrides.framework/PrivateHeaders/Private.h
index d52dd6c550ec9..0c4ed45702bca 100644
--- a/test/ClangImporter/Inputs/frameworks/CategoryOverrides.framework/PrivateHeaders/Private.h
+++ b/test/ClangImporter/Inputs/frameworks/CategoryOverrides.framework/PrivateHeaders/Private.h
@@ -14,3 +14,7 @@
 
 @interface MyBaseClass () <MyPrivateProtocol>
 @end
+
+@interface Refinery ()
+@property (nonatomic, readwrite) RefinedSugar sugar;
+@end
diff --git a/test/ClangImporter/objc_redeclared_properties_categories.swift b/test/ClangImporter/objc_redeclared_properties_categories.swift
index 0281251b87a75..7cf1ae534e37b 100644
--- a/test/ClangImporter/objc_redeclared_properties_categories.swift
+++ b/test/ClangImporter/objc_redeclared_properties_categories.swift
@@ -1,11 +1,11 @@
 // RUN: not %target-swift-frontend(mock-sdk: %clang-importer-sdk) -enable-objc-interop -typecheck -F %S/Inputs/frameworks %s 2>&1 | %FileCheck -check-prefix=CHECK -check-prefix=CHECK-PUBLIC %s
 
 // RUN: echo '#import <CategoryOverrides/Private.h>' > %t.h
-// RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) -typecheck -F %S/Inputs/frameworks -enable-objc-interop -import-objc-header %t.h %s 2>&1 | %FileCheck -check-prefix=CHECK -check-prefix=CHECK-PRIVATE %s --allow-empty
+// RUN: not %target-swift-frontend(mock-sdk: %clang-importer-sdk) -typecheck -F %S/Inputs/frameworks -enable-objc-interop -import-objc-header %t.h %s 2>&1 | %FileCheck -check-prefix=CHECK -check-prefix=CHECK-PRIVATE %s --allow-empty
 
 // RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) -enable-objc-interop -emit-pch -F %S/Inputs/frameworks -o %t.pch %t.h
-// RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) -typecheck -F %S/Inputs/frameworks -enable-objc-interop -import-objc-header %t.pch %s 2>&1 | %FileCheck --allow-empty -check-prefix=CHECK -check-prefix=CHECK-PRIVATE %s
-// RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) -typecheck -F %S/Inputs/frameworks -enable-objc-interop -import-objc-header %t.h -pch-output-dir %t/pch %s 2>&1 | %FileCheck --allow-empty -check-prefix=CHECK -check-prefix=CHECK-PRIVATE %s
+// RUN: not %target-swift-frontend(mock-sdk: %clang-importer-sdk) -typecheck -F %S/Inputs/frameworks -enable-objc-interop -import-objc-header %t.pch %s 2>&1 | %FileCheck --allow-empty -check-prefix=CHECK -check-prefix=CHECK-PRIVATE %s
+// RUN: not %target-swift-frontend(mock-sdk: %clang-importer-sdk) -typecheck -F %S/Inputs/frameworks -enable-objc-interop -import-objc-header %t.h -pch-output-dir %t/pch %s 2>&1 | %FileCheck --allow-empty -check-prefix=CHECK -check-prefix=CHECK-PRIVATE %s
 
 import CategoryOverrides
 
@@ -54,3 +54,27 @@ func takesABaseClass(_ x: MyBaseClass) {
   // CHECK-PRIVATE-NOT: has no member 'derivedMember'
   x.derivedMember = Base()
 }
+
+// A category declared in a (private) header can introduce overrides of a
+// property that has mismatched Swift naming conventions. If we see a
+// non-__attribute__((swift_private)) decl, sometimes it comes in too.
+
+extension Refinery {
+  public enum RefinedSugar {
+    case caster
+    case grantulated
+    case confectioners
+    case cane
+    case demerara
+    case turbinado
+  }
+
+  public var sugar: Refinery.RefinedSugar {
+    return .caster // RefinedSugar(self.__sugar)
+  }
+}
+
+func takesARefinery(_ x: Refinery) {
+  // CHECK: cannot assign to property: 'sugar' is a get-only property
+  x.sugar = .caster
+}