diff --git a/src/RwCalculators/GReWeightNuXSecCCQEvec.h b/src/RwCalculators/GReWeightNuXSecCCQEvec.h
index 4a7d7ca6..61e00fca 100644
--- a/src/RwCalculators/GReWeightNuXSecCCQEvec.h
+++ b/src/RwCalculators/GReWeightNuXSecCCQEvec.h
@@ -37,6 +37,7 @@ class TNtupleD;
 namespace genie {
 
 class XSecAlgorithmI;
+class XSecIntegratorI;
 
 namespace rew   {