diff --git a/configure.ac b/configure.ac
index b59d0751..ca8ecee3 100644
--- a/configure.ac
+++ b/configure.ac
@@ -390,7 +390,7 @@ void foo(const char *format, ...) {
 
        exit(0);
 }
-main() { foo("hello\n"); }
+int main() { foo("hello\n"); }
 ]])],[el_cv_HAVE_C99_VSNPRINTF=yes],[el_cv_HAVE_C99_VSNPRINTF=no],[el_cv_HAVE_C99_VSNPRINTF=cross])])
 if test x"$el_cv_HAVE_C99_VSNPRINTF" = x"yes"; then
 	EL_DEFINE(HAVE_C99_VSNPRINTF, [C99 compliant vsnprintf()])