diff --git a/IDEHelper/Compiler/BfExprEvaluator.cpp b/IDEHelper/Compiler/BfExprEvaluator.cpp
index 04417a8a..e97ab86a 100644
--- a/IDEHelper/Compiler/BfExprEvaluator.cpp
+++ b/IDEHelper/Compiler/BfExprEvaluator.cpp
@@ -18865,7 +18865,7 @@ bool BfExprEvaluator::CheckModifyResult(BfTypedValue& typedVal, BfAstNode* refNo
 					if (mModule->mCurMethodState->mMixinState != NULL)
 						error = _Fail(StrFormat("Cannot %s mixin parameter '%s'", modifyType,
 							localVar->mName.c_str()), refNode);
-					else if ((localVar->mResolvedType->IsGenericParam()) && (onlyNeedsMut))
+					else if ((onlyNeedsMut) && (localVar->mResolvedType != NULL) && (localVar->mResolvedType->IsGenericParam()))
 						error = _Fail(StrFormat("Cannot %s parameter '%s'. Consider adding 'mut' or 'ref' specifier to parameter or declaring 'var %s;' to create a mutable copy.", modifyType,
 							localVar->mName.c_str(), localVar->mName.c_str()), refNode);
 					else