diff --git a/lib/matplotlib/contour.py b/lib/matplotlib/contour.py
index 79f66b896131..7de45b54de38 100644
--- a/lib/matplotlib/contour.py
+++ b/lib/matplotlib/contour.py
@@ -887,10 +887,12 @@ def __init__(self, ax, *args,
         self.set_cmap(cmap)
         if norm is not None:
             self.set_norm(norm)
-        if vmin is not None:
-            self.norm.vmin = vmin
-        if vmax is not None:
-            self.norm.vmax = vmax
+        with self.norm.callbacks.blocked(signal="changed"):
+            if vmin is not None:
+                self.norm.vmin = vmin
+            if vmax is not None:
+                self.norm.vmax = vmax
+        self.norm._changed()
         self._process_colors()
 
         if self._paths is None: