diff --git a/src/cm.h b/src/cm.h
index 112bbfd020f..7f61912afa1 100644
--- a/src/cm.h
+++ b/src/cm.h
@@ -162,7 +162,7 @@ extern short ospeed;		/* Output speed (from sg_ospeed) */
 extern int cost;
 extern int evalcost ();
 
-extern void cmputc ();
+extern int cmputc ();
 extern int cmcostinit ();
 extern int cmgoto ();
 extern int Wcm_clear ();