diff --git a/src/vim9expr.c b/src/vim9expr.c
index 6fb32cb..a52f2c7 100644
--- a/src/vim9expr.c
+++ b/src/vim9expr.c
@@ -2716,7 +2716,8 @@
 	    if (tv2->vval.v_number > MAX_LSHIFT_BITS)
 		tv1->vval.v_number = 0;
 	    else if (type == EXPR_LSHIFT)
-		tv1->vval.v_number = tv1->vval.v_number << tv2->vval.v_number;
+		tv1->vval.v_number =
+			(uvarnumber_T)tv1->vval.v_number << tv2->vval.v_number;
 	    else
 		tv1->vval.v_number =
 			(uvarnumber_T)tv1->vval.v_number >> tv2->vval.v_number;