diff --git a/src/vim9execute.c b/src/vim9execute.c
index 5410aa2..217a977 100644
--- a/src/vim9execute.c
+++ b/src/vim9execute.c
@@ -4091,7 +4091,7 @@
 			case EXPR_LSHIFT: if (arg2 > MAX_LSHIFT_BITS)
 					      res = 0;
 					  else
-					      res = arg1 << arg2;
+					      res = (uvarnumber_T)arg1 << arg2;
 					  break;
 			case EXPR_RSHIFT: if (arg2 > MAX_LSHIFT_BITS)
 					      res = 0;