diff --git a/setup.py b/setup.py
index 644f289..6731c33 100644
--- a/setup.py
+++ b/setup.py
@@ -31,7 +31,7 @@ def read(fname):
       'dijkstra3d',
       sources=[ 'dijkstra3d.pyx' ],
       language='c++',
-      include_dirs=[ NumpyImport() ],
+      include_dirs=[ str(NumpyImport()) ],
       extra_compile_args=extra_compile_args,
     )
   ],