--- ./src/util/sys_defs.h.orig
+++ ./src/util/sys_defs.h
@@ -812,7 +812,7 @@
 #define KERNEL_VERSION(a,b,c) (LINUX_VERSION_CODE + 1)
 #endif
 #if (LINUX_VERSION_CODE < KERNEL_VERSION(2,2,0)) \
-	|| (__GLIBC__ < 2)
+	|| (defined(__GLIBC__) && (__GLIBC__ < 2))
 #define CANT_USE_SEND_RECV_MSG
 #define DEF_SMTP_CACHE_DEMAND	0
 #else
