--- a/client/keys.h
+++ b/client/keys.h
@@ -18,6 +18,9 @@
 
 */
 
+#ifndef _KEYS_H
+#define _KEYS_H
+
 //
 // these are the key numbers that should be passed to Key_Event
 //
@@ -121,3 +124,5 @@
 void Key_SetBinding (int keynum, char *binding);
 void Key_ClearStates (void);
 int Key_GetKey (void);
+
+#endif