diff --git a/configure.ac b/configure.ac
index 09ee123..b7b5908 100644
--- a/configure.ac
+++ b/configure.ac
@@ -7,8 +7,8 @@ m4_ifdef([AC_USE_SYSTEM_EXTENSIONS],
     [AC_USE_SYSTEM_EXTENSIONS],
     [AC_GNU_SOURCE])
 
-AC_PROG_CC_C89
-for flag in -std=c89 -Wall -Wextra; do
+AC_PROG_CC_C99
+for flag in -Wall -Wextra; do
   AC_TRY_COMPILE([], [return 0;], [CFLAGS="$CFLAGS $flag"],)
 done