diff --git a/bin/sh/arith_yacc.c b/bin/sh/arith_yacc.c
index fbf9a640c03..815d885eb6b 100644
--- a/bin/sh/arith_yacc.c
+++ b/bin/sh/arith_yacc.c
@@ -139,7 +139,7 @@ static arith_t do_binop(int op, arith_t a, arith_t b)
 	case ARITH_SUB:
 		return (uintmax_t)a - (uintmax_t)b;
 	case ARITH_LSHIFT:
-		return a << b;
+		return (uintmax_t)a << b;
 	case ARITH_RSHIFT:
 		return a >> b;
 	case ARITH_LT: