diff --git a/lib/matplotlib/colorbar.py b/lib/matplotlib/colorbar.py
index c23aa5cf4fd5..d8866d8e96bc 100644
--- a/lib/matplotlib/colorbar.py
+++ b/lib/matplotlib/colorbar.py
@@ -792,6 +792,9 @@ def _add_solids(self, X, Y, C):
 
     def _add_solids_pcolormesh(self, X, Y, C):
         _log.debug('Setting pcolormesh')
+        if C.shape[0] == Y.shape[0]:
+            # trim the last one to be compatible with old behavior.
+            C = C[:-1]
         self.solids = self.ax.pcolormesh(
             X, Y, C, cmap=self.cmap, norm=self.norm, alpha=self.alpha,
             edgecolors='none', shading='flat')