diff --git a/lib/matplotlib/colorbar.py b/lib/matplotlib/colorbar.py
index 0dc84edc2acc..4b2f86003eaa 100644
--- a/lib/matplotlib/colorbar.py
+++ b/lib/matplotlib/colorbar.py
@@ -788,6 +788,9 @@ def _add_solids(self, X, Y, C):
         Draw the colors using `~.axes.Axes.pcolormesh`;
         optionally add separators.
         """
+        if C.shape[0] == Y.shape[0]:
+            # trim the last one to be compatible with old behavior.
+            C = C[:-1]
         if self.orientation == 'vertical':
             args = (X, Y, C)
         else: