diff --git a/src/ast/ast.c b/src/ast/ast.c
index cae4c87..cbe1bd1 100644
--- a/src/ast/ast.c
+++ b/src/ast/ast.c
@@ -242,12 +242,19 @@ AST *ast_cast_expr(AST *what, Type *to) {
 		} else abort();
 	}
 	
+	bool copy = false;
+	
 	// Make sure an unparametrized generic int parameter hasn't sneaked its way in
 	while(what->nodeKind == AST_EXPR_VAR && what->exprVar.thing->kind == SCOPEITEM_CEXPR && what->exprVar.thing->data.cexpr.concrete) {
 		what = what->exprVar.thing->data.cexpr.concrete;
+		copy = true;
 	}
 	assert(!(what->nodeKind == AST_EXPR_VAR && what->exprVar.thing->kind == SCOPEITEM_CEXPR));
 	
+	if(copy) {
+		what = ast_deep_copy(what);
+	}
+	
 	if(type_equal(what->expression.type, to)) return what;
 	
 	if(!type_is_castable(what->expression.type, to)) {