diff --git a/cortex/__init__.py b/cortex/__init__.py
index 788a2d7ba..2475b312c 100644
--- a/cortex/__init__.py
+++ b/cortex/__init__.py
@@ -12,7 +12,9 @@
 try:
     from cortex import formats
 except ImportError:
-    raise ImportError("You are running pycortex from the source directory. Don't do that!")
+    raise ImportError("Either are running pycortex from the source directory, or the build is broken. "
+                      "If your current working directory is 'cortex', where pycortex is installed, then change this. "
+                      "If your current working directory is somewhere else, then you may have to rebuild pycortex.")
 
 load = Dataset.from_file