diff --git a/configure.ac b/configure.ac
index c93c613a..3ccd7db0 100644
--- a/configure.ac
+++ b/configure.ac
@@ -47,6 +47,7 @@ AC_C_BIGENDIAN
 
 dnl Checks for compiler
 AC_CHECK_CC_OPT([-Wall], CFLAGS="$CFLAGS -Wall", [])
+AC_CHECK_CC_OPT([-Wextra], CFLAGS="$CFLAGS -Wextra", [])
 
 AC_ARG_WITH([crypto],
 	[AS_HELP_STRING([--with-crypto],