diff --git a/lib/Analysis/PrintfFormatString.cpp b/lib/Analysis/PrintfFormatString.cpp
index b37b23f..e3d7650 100644
--- a/lib/Analysis/PrintfFormatString.cpp
+++ b/lib/Analysis/PrintfFormatString.cpp
@@ -290,7 +290,7 @@
 
   if (TypedefDecl *TD = dyn_cast_or_null<TypedefDecl>(D)) {
     QualType TypedefType = Ctx.getTypedefType(TD, QualType());
-    if (TD->getUnderlyingType() == Underlying)
+    if (Ctx.getCanonicalType(TypedefType) == Underlying)
       return TypedefType;
   }
 
diff --git a/test/Sema/format-strings-int-typedefs.c b/test/Sema/format-strings-int-typedefs.c
index 931449c..2cac9a8 100644
--- a/test/Sema/format-strings-int-typedefs.c
+++ b/test/Sema/format-strings-int-typedefs.c
@@ -10,7 +10,7 @@
   printf("%zu", 42.0); // expected-warning {{conversion specifies type 'unsigned long'}}
   printf("%td", 42.0); // expected-warning {{conversion specifies type 'int'}}
 
-  typedef __SIZE_TYPE__ size_t;
+  typedef __typeof(sizeof(int)) size_t;
   typedef __INTMAX_TYPE__ intmax_t;
   typedef __UINTMAX_TYPE__ uintmax_t;
   typedef __PTRDIFF_TYPE__ ptrdiff_t;