diff --git a/configure.ac b/configure.ac
index 372f2d1..757922e 100755
--- a/configure.ac
+++ b/configure.ac
@@ -574,6 +574,15 @@
 AM_CONDITIONAL([WITH_BOOSTTHREADS], [test "x[$]ENABLE_BOOSTTHREADS" = "x1"])
 
 AC_CONFIG_HEADERS(config.h:config.hin)
+# gruard against pre defined config.h
+AH_TOP([
+#ifndef CONFIG_H
+#define CONFIG_H 
+])
+AH_BOTTOM([
+#endif
+])
+
 
 AC_CONFIG_FILES([
   Makefile