Index: lib/Sema/SemaType.cpp
===================================================================
--- lib/Sema/SemaType.cpp
+++ lib/Sema/SemaType.cpp
@@ -5010,7 +5010,10 @@
         break;
       case DeclaratorChunk::Function: {
         const DeclaratorChunk::FunctionTypeInfo &FTI = DeclType.Fun;
-        if (FTI.NumParams == 0 && !FTI.isVariadic)
+        // We supress the warning when there's no LParen location, as this
+        // indicates the declaration was an implicit declaration, which gets
+        // warned about separately via -Wimplicit-function-declaration.
+        if (FTI.NumParams == 0 && !FTI.isVariadic && FTI.getLParenLoc().isValid())
           S.Diag(DeclType.Loc, diag::warn_strict_prototypes)
               << IsBlock
               << FixItHint::CreateInsertion(FTI.getRParenLoc(), "void");
Index: test/Sema/warn-strict-prototypes.c
===================================================================
--- test/Sema/warn-strict-prototypes.c
+++ test/Sema/warn-strict-prototypes.c
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -triple i386-pc-unknown -fsyntax-only -Wstrict-prototypes -verify %s
+// RUN: %clang_cc1 -triple i386-pc-unknown -fsyntax-only -Wstrict-prototypes -Wno-implicit-function-declaration -verify %s
 // RUN: %clang_cc1 -triple i386-pc-unknown -fsyntax-only -Wstrict-prototypes -fdiagnostics-parseable-fixits %s 2>&1 | FileCheck %s
 
 // function declaration with unspecified params
@@ -71,3 +71,9 @@
 // rdar://problem/33251668
 void foo13(...) __attribute__((overloadable));
 void foo13(...) __attribute__((overloadable)) {}
+
+// We should not generate a strict-prototype warning for an implicit
+// declaration.  Leave that up to the implicit-function-declaration warning.
+void foo14(void) {
+  foo14_call(); // no-warning
+}