diff --git a/synapticonn/monosynaptic_connections/ccg_synaptic_strength.py b/synapticonn/monosynaptic_connections/ccg_synaptic_strength.py
index 15f1edc..b314445 100644
--- a/synapticonn/monosynaptic_connections/ccg_synaptic_strength.py
+++ b/synapticonn/monosynaptic_connections/ccg_synaptic_strength.py
@@ -5,6 +5,7 @@
 """
 
 import warnings
+import math
 import numpy as np
 
 from joblib import Parallel, delayed