Index: lib/Sema/SemaDecl.cpp
===================================================================
--- lib/Sema/SemaDecl.cpp
+++ lib/Sema/SemaDecl.cpp
@@ -6496,8 +6496,7 @@
   // Check that the return type is not an abstract class type.
   // For record types, this is done by the AbstractClassUsageDiagnoser once
   // the class has been completely parsed.
-  if (!DC->isRecord() &&
-      SemaRef.RequireNonAbstractType(
+  if (SemaRef.RequireNonAbstractType(
           D.getIdentifierLoc(), R->getAs<FunctionType>()->getReturnType(),
           diag::err_abstract_type_in_decl, SemaRef.AbstractReturnType))
     D.setInvalidType();
Index: test/SemaCXX/abstract.cpp
===================================================================
--- test/SemaCXX/abstract.cpp
+++ test/SemaCXX/abstract.cpp
@@ -307,3 +307,14 @@
     RedundantInit() : A(0) {} // expected-warning {{initializer for virtual base class 'pr16659::A' of abstract class 'RedundantInit' will never be used}}
   };
 }
+
+namespace PR18393 {
+  struct A {
+      virtual void f() = 0;
+  };
+
+  struct B {
+      A f(); // expected-error {{return type 'PR18393::A' is an abstract class}}
+  };
+}
+