diff --git a/python/openEMS/_nf2ff.pxd b/python/openEMS/_nf2ff.pxd
index 859f062..cc70367 100644
--- a/python/openEMS/_nf2ff.pxd
+++ b/python/openEMS/_nf2ff.pxd
@@ -20,7 +20,7 @@ from libcpp.string cimport string
 from libcpp.vector cimport vector
 from libcpp.complex cimport complex
 from libcpp cimport bool
-cimport cython.numeric
+cimport cython
 
 cdef extern from "openEMS/nf2ff.h":
     cdef cppclass cpp_nf2ff "nf2ff":