diff --git a/modules/python/README.md b/modules/python/README.md
index 2ef025eb..5a51c3a3 100644
--- a/modules/python/README.md
+++ b/modules/python/README.md
@@ -9,9 +9,9 @@ This module will prepend the per user site packages directory as defined in [PEP
 man pages installed into the per user site.
 
 It also sources the [_virtualenvwrapper_][2] initialization script, if
-[_virtualenvwrapper_][2] is installed.  [_virtualenvwrapper_][2] is a frontend
-to [_virtualenv_][3] which provides convenient shell functions to create, switch
-and manage virtualenvs.
+[_virtualenvwrapper_][2] is installed and `$WORKON_HOME` is set.
+[_virtualenvwrapper_][2] is a frontend to [_virtualenv_][3] which provides
+convenient shell functions to create, switch and manage virtualenvs.
 
 Authors
 -------
diff --git a/modules/python/init.zsh b/modules/python/init.zsh
index 17120174..64fde25c 100644
--- a/modules/python/init.zsh
+++ b/modules/python/init.zsh
@@ -21,6 +21,8 @@ else
 fi
 
 # source virtualenvwrapper if available
-if (( $+commands[virtualenvwrapper.sh] )); then
-    source virtualenvwrapper.sh
+if (( $+WORKON_HOME )); then
+    if (( $+commands[virtualenvwrapper.sh] )); then
+        source virtualenvwrapper.sh
+    fi
 fi