diff --git a/configure.ac b/configure.ac
index c70c9f6f..e98b3b74 100644
--- a/configure.ac
+++ b/configure.ac
@@ -79,6 +79,7 @@ TEST_AND_ADD_CFLAGS([AM_CFLAGS], [-Wold-style-definition])
 TEST_AND_ADD_CFLAGS([AM_CFLAGS], [-Wparentheses-equality])
 TEST_AND_ADD_CFLAGS([AM_CFLAGS], [-Wshadow])
 TEST_AND_ADD_CFLAGS([AM_CFLAGS], [-Wshorten-64-to-32])
+TEST_AND_ADD_CFLAGS([AM_CFLAGS], [-Wundef])
 TEST_AND_ADD_CFLAGS([AM_CFLAGS], [-Wunreachable-code])
 TEST_AND_ADD_CFLAGS([AM_CFLAGS], [-Wunused-but-set-variable])
 TEST_AND_ADD_CFLAGS([AM_CFLAGS], [-Wunused])