diff --git a/src/github.com/matrix-org/dendrite/appservice/consumers/roomserver.go b/src/github.com/matrix-org/dendrite/appservice/consumers/roomserver.go
index bc1d3bf20..b3584dfb8 100644
--- a/src/github.com/matrix-org/dendrite/appservice/consumers/roomserver.go
+++ b/src/github.com/matrix-org/dendrite/appservice/consumers/roomserver.go
@@ -185,18 +185,9 @@ func (s *OutputRoomEventConsumer) appserviceIsInterestedInEvent(ctx context.Cont
 		return false
 	}
 
-	// Check sender of the event
-	for _, userNamespace := range appservice.NamespaceMap["users"] {
-		if userNamespace.RegexpObject.MatchString(event.Sender()) {
-			return true
-		}
-	}
-
-	// Check room id of the event
-	for _, roomNamespace := range appservice.NamespaceMap["rooms"] {
-		if roomNamespace.RegexpObject.MatchString(event.RoomID()) {
-			return true
-		}
+	if appservice.IsInterestedInUserID(event.Sender()) ||
+		appservice.IsInterestedInRoomID(event.RoomID()) {
+		return true
 	}
 
 	// Check all known room aliases of the room the event came from
@@ -204,10 +195,8 @@ func (s *OutputRoomEventConsumer) appserviceIsInterestedInEvent(ctx context.Cont
 	var queryRes api.GetAliasesForRoomIDResponse
 	if err := s.alias.GetAliasesForRoomID(ctx, &queryReq, &queryRes); err == nil {
 		for _, alias := range queryRes.Aliases {
-			for _, aliasNamespace := range appservice.NamespaceMap["aliases"] {
-				if aliasNamespace.RegexpObject.MatchString(alias) {
-					return true
-				}
+			if appservice.IsInterestedInRoomAlias(alias) {
+				return true
 			}
 		}
 	} else {
diff --git a/src/github.com/matrix-org/dendrite/clientapi/routing/register.go b/src/github.com/matrix-org/dendrite/clientapi/routing/register.go
index 76a696f93..813c4b3f9 100644
--- a/src/github.com/matrix-org/dendrite/clientapi/routing/register.go
+++ b/src/github.com/matrix-org/dendrite/clientapi/routing/register.go
@@ -337,17 +337,15 @@ func UsernameMatchesMultipleExclusiveNamespaces(
 ) bool {
 	// Check namespaces and see if more than one match
 	matchCount := 0
+	userID := userutil.MakeUserID(username, cfg.Matrix.ServerName)
 	for _, appservice := range cfg.Derived.ApplicationServices {
-		for _, namespaceSlice := range appservice.NamespaceMap {
-			for _, namespace := range namespaceSlice {
-				// Check if we have a match on this username
-				if namespace.RegexpObject.MatchString(username) {
-					matchCount++
-				}
+		if appservice.IsInterestedInUserID(userID) {
+			if matchCount++; matchCount > 1 {
+				return true
 			}
 		}
 	}
-	return matchCount > 1
+	return false
 }
 
 // validateApplicationService checks if a provided application service token
diff --git a/src/github.com/matrix-org/dendrite/common/config/appservice.go b/src/github.com/matrix-org/dendrite/common/config/appservice.go
index 178788e3c..2b47eb58d 100644
--- a/src/github.com/matrix-org/dendrite/common/config/appservice.go
+++ b/src/github.com/matrix-org/dendrite/common/config/appservice.go
@@ -66,6 +66,54 @@ type ApplicationService struct {
 	Protocols []string `yaml:"protocols"`
 }
 
+// IsInterestedInRoomID returns a bool on whether an application service's
+// namespace includes the given room ID
+func (a *ApplicationService) IsInterestedInRoomID(
+	roomID string,
+) bool {
+	if namespaceSlice, ok := a.NamespaceMap["rooms"]; ok {
+		for _, namespace := range namespaceSlice {
+			if namespace.RegexpObject.MatchString(roomID) {
+				return true
+			}
+		}
+	}
+
+	return false
+}
+
+// IsInterestedInUserID returns a bool on whether an application service's
+// namespace includes the given user ID
+func (a *ApplicationService) IsInterestedInUserID(
+	userID string,
+) bool {
+	if namespaceSlice, ok := a.NamespaceMap["users"]; ok {
+		for _, namespace := range namespaceSlice {
+			if namespace.RegexpObject.MatchString(userID) {
+				return true
+			}
+		}
+	}
+
+	return false
+}
+
+// IsInterestedInRoomAlias returns a bool on whether an application service's
+// namespace includes the given room alias
+func (a *ApplicationService) IsInterestedInRoomAlias(
+	roomAlias string,
+) bool {
+	if namespaceSlice, ok := a.NamespaceMap["aliases"]; ok {
+		for _, namespace := range namespaceSlice {
+			if namespace.RegexpObject.MatchString(roomAlias) {
+				return true
+			}
+		}
+	}
+
+	return false
+}
+
 // loadAppservices iterates through all application service config files
 // and loads their data into the config object for later access.
 func loadAppservices(config *Dendrite) error {