diff --git a/mongoose.h b/mongoose.h
index 2ed8fdb6..9b8b98b8 100644
--- a/mongoose.h
+++ b/mongoose.h
@@ -1432,6 +1432,8 @@ typedef struct stat cs_stat_t;
 #include <system_config.h>
 #include <system_definitions.h>
 
+#include <sys/types.h>
+
 typedef TCP_SOCKET sock_t;
 #define to64(x) strtoll(x, NULL, 10)