diff --git a/clang/lib/AST/RecordLayoutBuilder.cpp b/clang/lib/AST/RecordLayoutBuilder.cpp
--- a/clang/lib/AST/RecordLayoutBuilder.cpp
+++ b/clang/lib/AST/RecordLayoutBuilder.cpp
@@ -1066,7 +1066,6 @@
     EnsureVTablePointerAlignment(PtrAlign);
     HasOwnVFPtr = true;
 
-    assert(!IsUnion && "Unions cannot be dynamic classes.");
     HandledFirstNonOverlappingEmptyField = true;
 
     setSize(getSize() + PtrWidth);
@@ -1204,8 +1203,6 @@
 
 CharUnits
 ItaniumRecordLayoutBuilder::LayoutBase(const BaseSubobjectInfo *Base) {
-  assert(!IsUnion && "Unions cannot have base classes.");
-
   const ASTRecordLayout &Layout = Context.getASTRecordLayout(Base->Class);
   CharUnits Offset;
 
diff --git a/clang/test/SemaCXX/virtual-function-in-union.cpp b/clang/test/SemaCXX/virtual-function-in-union.cpp
--- a/clang/test/SemaCXX/virtual-function-in-union.cpp
+++ b/clang/test/SemaCXX/virtual-function-in-union.cpp
@@ -1,5 +1,8 @@
 // RUN: %clang_cc1 -fsyntax-only -verify %s
 
-union x {
-  virtual void f(); // expected-error {{unions cannot have virtual functions}}
+union U {
+  int d;
+  virtual int f() { return d; }; // expected-error {{unions cannot have virtual functions}}
 };
+
+int foo() { U u; return u.d; }