diff --git a/source/materials/OpticalMaterialProperties.cc b/source/materials/OpticalMaterialProperties.cc
index ec2bb2500..8bd6f192c 100644
--- a/source/materials/OpticalMaterialProperties.cc
+++ b/source/materials/OpticalMaterialProperties.cc
@@ -12,7 +12,6 @@
 
 #include <G4MaterialPropertiesTable.hh>
 
-#include <assert.h>
 
 using namespace nexus;
 using namespace CLHEP;