diff --git a/console/bridge.go b/console/bridge.go
index 467a19768d74..b977155ccf2d 100644
--- a/console/bridge.go
+++ b/console/bridge.go
@@ -19,6 +19,7 @@ package console
 import (
 	"encoding/json"
 	"errors"
+	"fmt"
 	"io"
 	"reflect"
 	"strings"
@@ -53,10 +54,11 @@ func (b *bridge) Sleep(call jsre.Call) (goja.Value, error) {
 	if nArgs := len(call.Arguments); nArgs < 1 {
 		return nil, errors.New("usage: sleep(<number of seconds>)")
 	}
-	if !isNumber(call.Argument(0)) {
-		return nil, errors.New("usage: sleep(<number of seconds>)")
+	sleepObj := call.Argument(0)
+	if goja.IsUndefined(sleepObj) || goja.IsNull(sleepObj) || !isNumber(sleepObj) {
+		return nil, fmt.Errorf("usage: sleep(<number of seconds>)")
 	}
-	sleep := call.Argument(0).ToFloat()
+	sleep := sleepObj.ToFloat()
 	time.Sleep(time.Duration(sleep * float64(time.Second)))
 	return call.VM.ToValue(true), nil
 }
@@ -74,13 +76,13 @@ func (b *bridge) SleepBlocks(call jsre.Call) (goja.Value, error) {
 		return nil, errors.New("usage: sleepBlocks(<n blocks>[, max sleep in seconds])")
 	}
 	if nArgs >= 1 {
-		if !isNumber(call.Argument(0)) {
+		if goja.IsNull(call.Argument(0)) || goja.IsUndefined(call.Argument(0)) || !isNumber(call.Argument(0)) {
 			return nil, errors.New("expected number as first argument")
 		}
 		blocks = call.Argument(0).ToInteger()
 	}
 	if nArgs >= 2 {
-		if !isNumber(call.Argument(1)) {
+		if goja.IsNull(call.Argument(1)) || goja.IsUndefined(call.Argument(1)) || !isNumber(call.Argument(1)) {
 			return nil, errors.New("expected number as second argument")
 		}
 		sleep = call.Argument(1).ToInteger()