diff --git a/test/PCH/preprocess.c b/test/PCH/preprocess.c
index bd91e5c..7a6c2c5 100644
--- a/test/PCH/preprocess.c
+++ b/test/PCH/preprocess.c
@@ -1,5 +1,8 @@
-// RUN: clang-cc -emit-pch -o %t %S/preprocess.h
-// RUN: clang-cc -include-pch %t -E -o - %s | grep -c "a_typedef" | count 1
-#include "preprocess.h"
+// Check that -E mode is invariant when using an implicit PCH.
 
-int a_value;
+// RUN: clang-cc -include %S/preprocess.h -E -o %t.orig %s
+// RUN: clang-cc -emit-pch -o %t %S/preprocess.h
+// RUN: clang-cc -include-pch %t -E -o %t.from_pch %s
+// RUN: diff %t.orig %t.from_pch
+
+a_typedef a_value;