diff --git a/snakehouse/constants.py b/snakehouse/constants.py
index 0afe778053d0e943d659f27cfaea01909e32cf5a..3f66461b474aabc0f402ee6f0af4dc71751c9f16 100644
--- a/snakehouse/constants.py
+++ b/snakehouse/constants.py
@@ -64,7 +64,7 @@ bootstrap_cython_submodules()
 """
 
 BOOTSTRAP_PYX_CDEF = """
-cdef extern from "%s"
+cdef extern from "%s":
     object PyInit_%s()    
 '"""