diff --git a/configure b/configure
index 5d21bcf3..594aa2a9 100755
--- a/configure
+++ b/configure
@@ -375,7 +375,7 @@ if ! echo "$cc" | grep -q "tcc"; then
   OPT1="-Wdeclaration-after-statement -fno-strict-aliasing"
   # we want -Wno- but gcc does not always reject unknown -Wno- options
   OPT2="-Wpointer-sign -Wsign-compare -Wunused-result -Wformat-truncation"
-  if echo "$cc" | grep -q "clang"; then
+  if $cc --version 2>&1 | grep -q "clang"; then
     OPT1="$OPT1 -fheinous-gnu-extensions"
     OPT2="$OPT2 -Wstring-plus-int"
   fi