diff --git a/configure.ac b/configure.ac
index b7c78e8b8..e8138e901 100644
--- a/configure.ac
+++ b/configure.ac
@@ -58,7 +58,7 @@ AC_PROG_CXX
 AC_C_INLINE
 if test "x$GCC" = "xyes" ; then
 
-    CFLAGS="-std=gnu99 -ggdb3 -Wall -W -Wpointer-arith -Wformat-security -Wcast-align -Wundef -Wcast-align -Wstrict-prototypes -Wmissing-declarations -Wmissing-format-attribute -Wredundant-decls -Wnested-externs -Wunreachable-code -Wunused-parameter -Wwrite-strings"
+    CFLAGS="$CFLAGS -std=gnu99 -ggdb3 -Wall -W -Wpointer-arith -Wformat-security -Wcast-align -Wundef -Wcast-align -Wstrict-prototypes -Wmissing-declarations -Wmissing-format-attribute -Wredundant-decls -Wnested-externs -Wunreachable-code -Wunused-parameter -Wwrite-strings"
 
     dnl figure out gcc version
     AC_MSG_CHECKING([gcc version])