diff --git a/configure.ac b/configure.ac
index cd242acd31..3af5804355 100644
--- a/configure.ac
+++ b/configure.ac
@@ -308,10 +308,10 @@ dnl set location of plugin directory
 AG_GST_SET_PLUGINDIR
 
 dnl define an ERROR_CFLAGS Makefile variable
-AG_GST_SET_ERROR_CFLAGS($GST_GIT, [-Wmissing-declarations -Wmissing-prototypes -Wredundant-decls])
+AG_GST_SET_ERROR_CFLAGS($GST_GIT, [-Wmissing-declarations -Wmissing-prototypes -Wredundant-decls -Wundef])
 
 dnl define an ERROR_CXXFLAGS Makefile variable
-AG_GST_SET_ERROR_CXXFLAGS($GST_GIT, [-Wmissing-declarations -Wmissing-prototypes -Wredundant-decls])
+AG_GST_SET_ERROR_CXXFLAGS($GST_GIT, [-Wmissing-declarations -Wmissing-prototypes -Wredundant-decls -Wundef])
 
 dnl define correct level for debugging messages
 AG_GST_SET_LEVEL_DEFAULT($GST_GIT)