diff --git a/lib/Frontend/Warnings.cpp b/lib/Frontend/Warnings.cpp
index 6f44111..576dd3d 100644
--- a/lib/Frontend/Warnings.cpp
+++ b/lib/Frontend/Warnings.cpp
@@ -83,6 +83,10 @@
     for (unsigned i = 0, e = Opts.Warnings.size(); i != e; ++i) {
       StringRef Opt = Opts.Warnings[i];
 
+      // Treat -Wformat=0 as an alias for -Wno-format.
+      if (Opt == "format=0")
+        Opt = "no-format";
+
       // Check to see if this warning starts with "no-", if so, this is a
       // negative form of the option.
       bool isPositive = true;
diff --git a/test/Sema/format-strings-scanf.c b/test/Sema/format-strings-scanf.c
index 4d9843c..be70357 100644
--- a/test/Sema/format-strings-scanf.c
+++ b/test/Sema/format-strings-scanf.c
@@ -1,5 +1,8 @@
 // RUN: %clang_cc1 -fsyntax-only -verify -triple i386-apple-darwin9 -Wformat-nonliteral %s
 
+// Test that -Wformat=0 works:
+// RUN: %clang_cc1 -fsyntax-only -Werror -Wformat=0 %s
+
 #include <stdarg.h>
 typedef __typeof(sizeof(int)) size_t;
 typedef struct _FILE FILE;