--- a/PDSim/core/_core.pxd
+++ b/PDSim/core/_core.pxd
@@ -1,8 +1,5 @@
 import cython
 cimport cython
-
-#Import the listm type used in PDSim
-from PDSim.misc._listmath cimport listm
 
 cdef class _PDSimCore:
     pass