diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
index 47a84927268f..adbcafe4339d 100644
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -1905,6 +1905,12 @@ void Sema::DiagnoseAbsenceOfOverrideControl(NamedDecl *D) {
       isa<CXXDestructorDecl>(MD))
     return;
 
+  if (MD->getLocation().isMacroID()) {
+    SourceLocation MacroLoc = getSourceManager().getSpellingLoc(MD->getLocation());
+    if (getSourceManager().isInSystemHeader(MacroLoc))
+      return;
+  }
+  
   if (MD->size_overridden_methods() > 0) {
     Diag(MD->getLocation(), diag::warn_function_marked_not_override_overriding)
       << MD->getDeclName();
diff --git a/clang/test/SemaCXX/Inputs/override-system-header.h b/clang/test/SemaCXX/Inputs/override-system-header.h
new file mode 100644
index 000000000000..9a1bde5a26b3
--- /dev/null
+++ b/clang/test/SemaCXX/Inputs/override-system-header.h
@@ -0,0 +1,3 @@
+// override-system-header.h to test out 'override' warning.
+// rdar://18295240
+#define END_COM_MAP virtual unsigned AddRef(void) = 0;
diff --git a/clang/test/SemaCXX/override-in-system-header.cpp b/clang/test/SemaCXX/override-in-system-header.cpp
new file mode 100644
index 000000000000..88c53e4430a4
--- /dev/null
+++ b/clang/test/SemaCXX/override-in-system-header.cpp
@@ -0,0 +1,17 @@
+// RUN: %clang_cc1 -std=c++11 -isystem %S/Inputs %s -verify
+// expected-no-diagnostics
+// rdar://18295240
+
+#include <override-system-header.h>
+
+struct A
+{
+  virtual void x();
+  END_COM_MAP;
+};
+ 
+struct B : A
+{
+  virtual void x() override;
+  END_COM_MAP;
+};