diff --git a/codes/codes.go b/codes/codes.go
index a8280ae6..d9b9d578 100644
--- a/codes/codes.go
+++ b/codes/codes.go
@@ -22,6 +22,7 @@ package codes // import "google.golang.org/grpc/codes"
 
 import (
 	"fmt"
+	"strconv"
 )
 
 // A Code is an unsigned 32-bit error code as defined in the gRPC spec.
@@ -143,6 +144,8 @@ const (
 	// Unauthenticated indicates the request does not have valid
 	// authentication credentials for the operation.
 	Unauthenticated Code = 16
+
+	_maxCode = 17
 )
 
 var strToCode = map[string]Code{
@@ -176,6 +179,16 @@ func (c *Code) UnmarshalJSON(b []byte) error {
 	if c == nil {
 		return fmt.Errorf("nil receiver passed to UnmarshalJSON")
 	}
+
+	if ci, err := strconv.ParseUint(string(b), 10, 32); err == nil {
+		if ci >= _maxCode {
+			return fmt.Errorf("invalid code: %q", ci)
+		}
+
+		*c = Code(ci)
+		return nil
+	}
+
 	if jc, ok := strToCode[string(b)]; ok {
 		*c = jc
 		return nil
diff --git a/codes/codes_test.go b/codes/codes_test.go
index 1e3b9918..d3e32d22 100644
--- a/codes/codes_test.go
+++ b/codes/codes_test.go
@@ -62,3 +62,23 @@ func TestUnmarshalJSON_UnknownInput(t *testing.T) {
 		}
 	}
 }
+
+func TestUnmarshalJSON_MarshalUnmarshal(t *testing.T) {
+	for i := 0; i < _maxCode; i++ {
+		var cUnMarshaled Code
+		c := Code(i)
+
+		cJSON, err := json.Marshal(c)
+		if err != nil {
+			t.Errorf("marshalling %q failed: %v", c, err)
+		}
+
+		if err := json.Unmarshal(cJSON, &cUnMarshaled); err != nil {
+			t.Errorf("unmarshalling code failed: %s", err)
+		}
+
+		if c != cUnMarshaled {
+			t.Errorf("code is %q after marshalling/unmarshalling, expected %q", cUnMarshaled, c)
+		}
+	}
+}