diff --git a/eventcontent_test.go b/eventcontent_test.go
index ee13de4c..53920851 100644
--- a/eventcontent_test.go
+++ b/eventcontent_test.go
@@ -217,11 +217,13 @@ func TestMXIDMapping_SignValidate(t *testing.T) {
 	assert.NoError(t, err)
 
 	// this should pass
-	err = validateMXIDMappingSignature(context.Background(), ev, &StubVerifier{}, verImpl)
+	evMapping, err := getMXIDMapping(ev)
+	assert.NoError(t, err)
+	err = validateMXIDMappingSignatures(context.Background(), ev, *evMapping, &StubVerifier{}, verImpl)
 	assert.NoError(t, err)
 
 	// this fails, for some random reason
-	err = validateMXIDMappingSignature(context.Background(), ev, &StubVerifier{
+	err = validateMXIDMappingSignatures(context.Background(), ev, *evMapping, &StubVerifier{
 		results: []VerifyJSONResult{{Error: fmt.Errorf("err")}},
 	}, verImpl)
 	assert.Error(t, err)
@@ -231,7 +233,6 @@ func TestMXIDMapping_SignValidate(t *testing.T) {
 	ev, err = eb.Build(time.Now(), serverName, keyID, priv)
 	assert.NoError(t, err)
 
-	err = validateMXIDMappingSignature(context.Background(), ev, &StubVerifier{}, verImpl)
+	_, err = getMXIDMapping(ev)
 	assert.Error(t, err)
-
 }
diff --git a/eventcrypto.go b/eventcrypto.go
index cc30f2c1..6d4a7add 100644
--- a/eventcrypto.go
+++ b/eventcrypto.go
@@ -85,7 +85,11 @@ func VerifyEventSignatures(ctx context.Context, e PDU, verifier JSONVerifier, us
 
 		// Validate the MXIDMapping is signed correctly
 		if verImpl.Version() == RoomVersionPseudoIDs && membership == spec.Join {
-			err = validateMXIDMappingSignature(ctx, e, verifier, verImpl)
+			mapping, err := getMXIDMapping(e)
+			if err != nil {
+				return err
+			}
+			err = validateMXIDMappingSignatures(ctx, e, *mapping, verifier, verImpl)
 			if err != nil {
 				return err
 			}
@@ -154,28 +158,32 @@ func VerifyEventSignatures(ctx context.Context, e PDU, verifier JSONVerifier, us
 	return nil
 }
 
-// validateMXIDMappingSignature validates that the MXIDMapping is correctly signed
-func validateMXIDMappingSignature(ctx context.Context, e PDU, verifier JSONVerifier, verImpl IRoomVersion) error {
+func getMXIDMapping(e PDU) (*MXIDMapping, error) {
 	var content MemberContent
 	err := json.Unmarshal(e.Content(), &content)
 	if err != nil {
-		return err
+		return nil, err
 	}
 
 	// if there is no mapping, we can't check the signature
 	if content.MXIDMapping == nil {
-		return fmt.Errorf("missing mxid_mapping, unable to validate event")
+		return nil, fmt.Errorf("missing mxid_mapping")
 	}
 
-	var toVerify []VerifyJSONRequest
+	return content.MXIDMapping, nil
+}
 
-	mapping, err := json.Marshal(content.MXIDMapping)
+// validateMXIDMappingSignatures validates that the MXIDMapping is correctly signed
+func validateMXIDMappingSignatures(ctx context.Context, e PDU, mapping MXIDMapping, verifier JSONVerifier, verImpl IRoomVersion) error {
+	mappingBytes, err := json.Marshal(mapping)
 	if err != nil {
 		return err
 	}
-	for s := range content.MXIDMapping.Signatures {
+
+	var toVerify []VerifyJSONRequest
+	for s := range mapping.Signatures {
 		v := VerifyJSONRequest{
-			Message:              mapping,
+			Message:              mappingBytes,
 			AtTS:                 e.OriginServerTS(),
 			ServerName:           s,
 			ValidityCheckingFunc: verImpl.SignatureValidityCheck,
diff --git a/handlejoin.go b/handlejoin.go
index 468d209d..56234995 100644
--- a/handlejoin.go
+++ b/handlejoin.go
@@ -22,7 +22,6 @@ import (
 
 	"github.com/matrix-org/gomatrixserverlib/spec"
 	"github.com/matrix-org/util"
-	"github.com/tidwall/gjson"
 )
 
 type HandleMakeJoinInput struct {
@@ -351,15 +350,14 @@ func HandleSendJoin(input HandleSendJoinInput) (*HandleSendJoinResponse, error)
 	// validate the mxid_mapping of the event
 	if input.RoomVersion == RoomVersionPseudoIDs {
 		// validate the signature first
-		if err = validateMXIDMappingSignature(input.Context, event, input.Verifier, verImpl); err != nil {
+		mapping, err := getMXIDMapping(event)
+		if err != nil {
+			return nil, spec.BadJSON(err.Error())
+		}
+		if err = validateMXIDMappingSignatures(input.Context, event, *mapping, input.Verifier, verImpl); err != nil {
 			return nil, spec.Forbidden(err.Error())
 		}
 
-		mapping := MXIDMapping{}
-		err = json.Unmarshal([]byte(gjson.GetBytes(input.JoinEvent, "content.mxid_mapping").Raw), &mapping)
-		if err != nil {
-			return nil, err
-		}
 		// store the user room public key -> userID mapping
 		if err = input.StoreSenderIDFromPublicID(input.Context, mapping.UserRoomKey, mapping.UserID, input.RoomID); err != nil {
 			return nil, err
diff --git a/performjoin.go b/performjoin.go
index ce76bf59..db480d5a 100644
--- a/performjoin.go
+++ b/performjoin.go
@@ -304,20 +304,17 @@ func storeMXIDMappings(
 		if ev.Type() != spec.MRoomMember {
 			continue
 		}
-		mapping := MemberContent{}
-		if err := json.Unmarshal(ev.Content(), &mapping); err != nil {
+		mapping, err := getMXIDMapping(ev)
+		if err != nil {
 			return err
 		}
-		if mapping.MXIDMapping == nil {
-			continue
-		}
 		// we already validated it is a valid roomversion, so this should be safe to use.
 		verImpl := MustGetRoomVersion(ev.Version())
-		if err := validateMXIDMappingSignature(ctx, ev, keyRing, verImpl); err != nil {
+		if err := validateMXIDMappingSignatures(ctx, ev, *mapping, keyRing, verImpl); err != nil {
 			logrus.WithError(err).Error("invalid signature for mxid_mapping")
 			continue
 		}
-		if err := storeSenderID(ctx, ev.SenderID(), mapping.MXIDMapping.UserID, roomID); err != nil {
+		if err := storeSenderID(ctx, ev.SenderID(), mapping.UserID, roomID); err != nil {
 			return err
 		}
 	}