diff --git a/clang/lib/Basic/Diagnostic.cpp b/clang/lib/Basic/Diagnostic.cpp
--- a/clang/lib/Basic/Diagnostic.cpp
+++ b/clang/lib/Basic/Diagnostic.cpp
@@ -374,6 +374,12 @@
   DiagnosticMapping Mapping = makeUserMapping(Map, L);
   Mapping.setUpgradedFromWarning(WasUpgradedFromWarning);
 
+  // Make sure we propagate the NoWarningAsError flag from an existing
+  // mapping (which may be the default mapping).
+  DiagnosticMapping &Info = GetCurDiagState()->getOrAddMapping(Diag);
+  Mapping.setNoWarningAsError(Info.hasNoWarningAsError() ||
+                              Mapping.hasNoWarningAsError());
+
   // Common case; setting all the diagnostics of a group in one place.
   if ((L.isInvalid() || L == DiagStatesByLoc.getCurDiagStateLoc()) &&
       DiagStatesByLoc.getCurDiagState()) {
diff --git a/clang/test/Lexer/pragma-message.c b/clang/test/Lexer/pragma-message.c
--- a/clang/test/Lexer/pragma-message.c
+++ b/clang/test/Lexer/pragma-message.c
@@ -1,6 +1,5 @@
 /* Test pragma message directive from
    http://msdn.microsoft.com/en-us/library/x7dkzch2.aspx */
-
 // message: Sends a string literal to the standard output without terminating
 // the compilation.
 // #pragma message(messagestring)
@@ -8,6 +7,7 @@
 // #pragma message messagestring
 //
 // RUN: %clang_cc1 -fsyntax-only -verify -Werror %s
+// RUN: %clang_cc1 -fsyntax-only -verify -Werror -W#pragma-messages %s
 #define STRING2(x) #x
 #define STRING(x) STRING2(x)
 #pragma message(":O I'm a message! " STRING(__LINE__)) // expected-warning {{:O I'm a message! 13}}