diff --git a/src/encoding/json/decode.go b/src/encoding/json/decode.go
index cab4616ba3..6608415e13 100644
--- a/src/encoding/json/decode.go
+++ b/src/encoding/json/decode.go
@@ -786,7 +786,7 @@ func (d *decodeState) object(v reflect.Value) error {
 					n, err := strconv.ParseInt(s, 10, 64)
 					if err != nil || reflect.Zero(kt).OverflowInt(n) {
 						d.saveError(&UnmarshalTypeError{Value: "number " + s, Type: kt, Offset: int64(start + 1)})
-						return nil
+						break
 					}
 					kv = reflect.ValueOf(n).Convert(kt)
 				case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
@@ -794,14 +794,16 @@ func (d *decodeState) object(v reflect.Value) error {
 					n, err := strconv.ParseUint(s, 10, 64)
 					if err != nil || reflect.Zero(kt).OverflowUint(n) {
 						d.saveError(&UnmarshalTypeError{Value: "number " + s, Type: kt, Offset: int64(start + 1)})
-						return nil
+						break
 					}
 					kv = reflect.ValueOf(n).Convert(kt)
 				default:
 					panic("json: Unexpected key type") // should never occur
 				}
 			}
-			v.SetMapIndex(kv, subv)
+			if kv.IsValid() {
+				v.SetMapIndex(kv, subv)
+			}
 		}
 
 		// Next token must be , or }.
diff --git a/src/encoding/json/decode_test.go b/src/encoding/json/decode_test.go
index 5fbe67a706..70731a62d6 100644
--- a/src/encoding/json/decode_test.go
+++ b/src/encoding/json/decode_test.go
@@ -554,6 +554,16 @@ var unmarshalTests = []unmarshalTest{
 		ptr: new(map[uint8]string),
 		err: &UnmarshalTypeError{Value: "number -1", Type: reflect.TypeOf(uint8(0)), Offset: 2},
 	},
+	{
+		in:  `{"F":{"a":2,"3":4}}`,
+		ptr: new(map[string]map[int]int),
+		err: &UnmarshalTypeError{Value: "number a", Type: reflect.TypeOf(int(0)), Offset: 7},
+	},
+	{
+		in:  `{"F":{"a":2,"3":4}}`,
+		ptr: new(map[string]map[uint]int),
+		err: &UnmarshalTypeError{Value: "number a", Type: reflect.TypeOf(uint(0)), Offset: 7},
+	},
 
 	// Map keys can be encoding.TextUnmarshalers.
 	{in: `{"x:y":true}`, ptr: &ummapType, out: ummapXY},