diff --git a/lib/iris/tests/__init__.py b/lib/iris/tests/__init__.py
index 8dcc0e136c..5529990dd0 100644
--- a/lib/iris/tests/__init__.py
+++ b/lib/iris/tests/__init__.py
@@ -139,7 +139,7 @@
     plt.switch_backend('tkagg')
     _DISPLAY_FIGURES = True
 
-_DEFAULT_IMAGE_TOLERANCE = 10.0
+_DEFAULT_IMAGE_TOLERANCE = 0.1
 
 
 def main():