diff --git a/lib/matplotlib/image.py b/lib/matplotlib/image.py
index a9088a78af5a..0056203b08f5 100644
--- a/lib/matplotlib/image.py
+++ b/lib/matplotlib/image.py
@@ -114,7 +114,7 @@ def __init__(self, ax,
     def __getstate__(self):
         state = super(_AxesImageBase, self).__getstate__()
         # We can't pickle the C Image cached object.
-        state.pop('_imcache', None)
+        state['_imcache'] = None
         return state
 
     def get_size(self):