diff --git a/contrib/space-invaders/cpu-8080.factor b/contrib/space-invaders/cpu-8080.factor
index fac2e84270..f1630f86af 100644
--- a/contrib/space-invaders/cpu-8080.factor
+++ b/contrib/space-invaders/cpu-8080.factor
@@ -465,7 +465,7 @@ M: cpu reset ( cpu -- )
   [ HEX: 10 swap set-cpu-last-interrupt ] keep
   0 swap set-cpu-cycles ;
 
-C: cpu ( cpu -- cpu )
+C: cpu ( -- cpu )
   [ reset ] keep ;
 
 : (load-rom) ( n ram -- )
@@ -573,7 +573,7 @@ C: cpu ( cpu -- cpu )
 : test-n ( n -- )
   test-cpu swap [ test-step ] times ;
 
-: run-n ( cpu n -- )
+: run-n ( cpu n -- cpu )
   [ dup step ] times ;
 
 : register-lookup ( string -- vector )
diff --git a/contrib/space-invaders/space-invaders.factor b/contrib/space-invaders/space-invaders.factor
index 7ccee94ae6..9a624568e4 100644
--- a/contrib/space-invaders/space-invaders.factor
+++ b/contrib/space-invaders/space-invaders.factor
@@ -59,7 +59,7 @@ TUPLE: space-invaders port1 port2i port2o port3o port4lo port4hi port5o bitmap ;
   [ [ 1 + ] dip uchar-nth ] 2keep
   [ 2 + ] dip uchar-nth 3array ;
   
-C: space-invaders ( cpu -- cpu )
+C: space-invaders ( -- cpu )
   [ <cpu> swap set-delegate ] keep
   [ make-opengl-bitmap swap set-space-invaders-bitmap ] keep
   [ reset ] keep ;