--- a/configure.ac
+++ b/configure.ac
@@ -2879,6 +2879,7 @@ CURL_VERIFY_RUNTIMELIBS
 
 AC_CHECK_SIZEOF(size_t)
 AC_CHECK_SIZEOF(long)
+AC_CHECK_SIZEOF(long long)
 AC_CHECK_SIZEOF(int)
 AC_CHECK_SIZEOF(short)
 CURL_CONFIGURE_LONG