diff --git a/Cocoa/GBView.h b/Cocoa/GBView.h
index c19d340..80721cd 100644
--- a/Cocoa/GBView.h
+++ b/Cocoa/GBView.h
@@ -22,5 +22,5 @@ typedef enum {
 - (uint32_t *)currentBuffer;
 - (uint32_t *)previousBuffer;
 - (void)screenSizeChanged;
-- (void)setRumble: (bool)on;
+- (void)setRumble: (double)amp;
 @end
diff --git a/Cocoa/GBView.m b/Cocoa/GBView.m
index 1272c93..e733731 100644
--- a/Cocoa/GBView.m
+++ b/Cocoa/GBView.m
@@ -270,9 +270,9 @@
     }
 }
 
-- (void)setRumble:(bool)on
+- (void)setRumble:(double)amp
 {
-    [lastController setRumbleAmplitude:(double)on];
+    [lastController setRumbleAmplitude:amp];
 }
 
 - (void)controller:(JOYController *)controller movedAxis:(JOYAxis *)axis