diff --git a/lib/Lex/PPMacroExpansion.cpp b/lib/Lex/PPMacroExpansion.cpp
index 20ebb40f53..5cd656527b 100644
--- a/lib/Lex/PPMacroExpansion.cpp
+++ b/lib/Lex/PPMacroExpansion.cpp
@@ -116,6 +116,11 @@ static bool isTrivialSingleTokenExpansion(const MacroInfo *MI,
   // If the token isn't an identifier, it's always literally expanded.
   if (II == 0) return true;
 
+  // If the information about this identifier is out of date, update it from
+  // the external source.
+  if (II->isOutOfDate())
+    PP.getExternalSource()->updateOutOfDateIdentifier(*II);
+
   // If the identifier is a macro, and if that macro is enabled, it may be
   // expanded so it's not a trivial expansion.
   if (II->hasMacroDefinition() && PP.getMacroInfo(II)->isEnabled() &&
diff --git a/test/PCH/single-token-macro.c b/test/PCH/single-token-macro.c
new file mode 100644
index 0000000000..104dc130f6
--- /dev/null
+++ b/test/PCH/single-token-macro.c
@@ -0,0 +1,26 @@
+// rdar://10588825
+
+// Test this without pch.
+// RUN: %clang_cc1 %s -include %s -verify -fsyntax-only
+
+// Test with pch.
+// RUN: %clang_cc1 %s -emit-pch -o %t
+// RUN: %clang_cc1 %s -include-pch %t -verify -fsyntax-only
+
+#ifndef HEADER
+#define HEADER
+
+#define SKATA
+
+#define __stdcall
+#define STDCALL __stdcall
+
+void STDCALL Foo(void);
+
+#else
+
+void STDCALL Foo(void)
+{
+}
+
+#endif