diff --git a/configure.ac b/configure.ac
index 690c4bc..03ebdbf 100644
--- a/configure.ac
+++ b/configure.ac
@@ -14,6 +14,7 @@ AC_LANG([C]) # Use C not C++
 
 # Checks for programs.
 AC_PROG_CC
+AC_PROG_CC_C99 # or AC_PROG_CC_89 to force C89 mode or AC_PROG_CC_STDC to go to latest supported standard (currently C99)
 
 # In case that you want to check for specific versions of gcc 
 # For example in case that you need C11 support you want to