diff --git a/go/vt/vtgate/evalengine/compiler_asm.go b/go/vt/vtgate/evalengine/compiler_asm.go
index 161e3525b5d..1a750ed7d0e 100644
--- a/go/vt/vtgate/evalengine/compiler_asm.go
+++ b/go/vt/vtgate/evalengine/compiler_asm.go
@@ -3784,11 +3784,12 @@ func (asm *assembler) Fn_LAST_DAY() {
 			return 1
 		}
 		arg := env.vm.stack[env.vm.sp-1].(*evalTemporal)
-		d := lastDay(env.currentTimezone(), arg.dt)
-		if d.IsZero() {
+		if arg.dt.IsZero() {
 			env.vm.stack[env.vm.sp-1] = nil
 			return 1
 		}
+
+		d := lastDay(env.currentTimezone(), arg.dt)
 		env.vm.stack[env.vm.sp-1] = env.vm.arena.newEvalDate(d)
 		return 1
 	}, "FN LAST_DAY DATETIME(SP-1)")
diff --git a/go/vt/vtgate/evalengine/fn_time.go b/go/vt/vtgate/evalengine/fn_time.go
index 45fa5ad447e..de1b7259aff 100644
--- a/go/vt/vtgate/evalengine/fn_time.go
+++ b/go/vt/vtgate/evalengine/fn_time.go
@@ -1228,10 +1228,6 @@ func (b *builtinLastDay) eval(env *ExpressionEnv) (eval, error) {
 	}
 
 	d := lastDay(env.currentTimezone(), dt.dt)
-	if d.IsZero() {
-		return nil, nil
-	}
-
 	return newEvalDate(d, env.sqlmode.AllowZeroDate()), nil
 }