diff --git a/docs/source/conf.py b/docs/source/conf.py
index be7e3a8d13..22446213af 100644
--- a/docs/source/conf.py
+++ b/docs/source/conf.py
@@ -53,9 +53,10 @@ extensions = ['sphinx.ext.autodoc',
               'sphinx.ext.autosummary',
               'sphinx.ext.intersphinx',
               'sphinx.ext.viewcode',
-              'sphinx.ext.imgconverter',
               'sphinx_numfig',
               'notebook_sphinxext']
+if not on_rtd:
+    extensions.append('sphinx.ext.imgconverter')
 
 # Add any paths that contain templates here, relative to this directory.
 templates_path = ['_templates']