diff --git a/lib/matplotlib/pyplot.py b/lib/matplotlib/pyplot.py
index cbb49a94a999..445952f51847 100644
--- a/lib/matplotlib/pyplot.py
+++ b/lib/matplotlib/pyplot.py
@@ -1737,13 +1737,13 @@ def set_cmap(cmap):
     '''
     cmap = cm.get_cmap(cmap)
 
+    # set the default colormap
     rc('image', cmap=cmap.name)
+    
+    # apply to current image if any
     im = gci()
-
     if im is not None:
         im.set_cmap(cmap)
-    else:
-        raise RuntimeError('You must first define an image, eg with imshow')
 
     draw_if_interactive()