diff --git a/preprocessor/SymbolTable.cc b/preprocessor/SymbolTable.cc
index 97b98430499cfc189341457fd3d41b69b5689000..0015268433bb5b3f10c31281bf4337bdaa5cfbc3 100644
--- a/preprocessor/SymbolTable.cc
+++ b/preprocessor/SymbolTable.cc
@@ -329,6 +329,7 @@ SymbolTable::writeCOutput(ostream &output) const throw (NotYetFrozenException)
           case avExoLead:
           case avExpectation:
           case avMultiplier:
+          case avDiffForward:
             break;
           case avEndoLag:
           case avExoLag: