diff --git a/configure.ac b/configure.ac
index bd6e0be..2324e7d 100644
--- a/configure.ac
+++ b/configure.ac
@@ -15,7 +15,7 @@ LT_INIT([pic-only])
 
 # fix std
 CC=$(echo "${CC}" | sed 's/-std=gnu99/-std=c99/')
-CPP=$(echo "${CC}" | sed 's/-std=gnu99/-std=c99/')
+CPP=$(echo "${CPP}" | sed 's/-std=gnu99/-std=c99/')
 
 # Checks for libraries.
 AC_SEARCH_LIBS([gcry_check_version], [gcrypt], [], [AC_MSG_ERROR([unable to find the gcry_check_version() function from libgcrypt])])