diff --git a/bridge/irc/handlers.go b/bridge/irc/handlers.go
index 886e20df..e3900f3a 100644
--- a/bridge/irc/handlers.go
+++ b/bridge/irc/handlers.go
@@ -113,7 +113,7 @@ func (b *Birc) handleJoinPart(client *girc.Client, event girc.Event) {
 			return
 		} else if b.GetBool("nosendjoinpart") {
 			return
-		} else if b.isUserActive(event.Source.Name) || isKill(event.Last()) {
+		} else if isActive, _ := b.isUserActive(event.Source.Name); isActive || isKill(event.Last()) {
 			verbosequit := ""
 			quitmsg := ""
 			if len(event.Params) >= 1 {
@@ -129,7 +129,7 @@ func (b *Birc) handleJoinPart(client *girc.Client, event girc.Event) {
 		}
 	}
 	if event.Source.Name != b.Nick {
-		if b.GetBool("nosendjoinpart") || !b.isUserActive(event.Source.Name) {
+		if isActive, _ := b.isUserActive(event.Source.Name); !isActive || b.GetBool("nosendjoinpart") {
 			return
 		}
 		partmsg := ""
@@ -171,7 +171,7 @@ func (b *Birc) handleNick(client *girc.Client, event girc.Event) {
 	if len(event.Params) != 1 {
 		b.Log.Debugf("handleJoinPart: malformed nick change? %#v", event)
 		return
-	} else if b.isUserActive(event.Source.Name) {
+	} else if isActive, activeTime := b.isUserActive(event.Source.Name); isActive {
 		msg := config.Message{Username: "system",
 			Text:    event.Source.Name + " changed nick to " + event.Params[0],
 			Channel: b.getPseudoChannel(),
@@ -181,7 +181,7 @@ func (b *Birc) handleNick(client *girc.Client, event girc.Event) {
 		b.Remote <- msg
 		if b.ActivityTimeout != 0 {
 			// This doesn't count as new activity, but it does preserve the value
-			b.activeUsers[event.Params[0]] = b.activeUsers[event.Source.Name]
+			b.markUserActive(event.Params[0], activeTime)
 		}
 	}
 }
@@ -293,7 +293,7 @@ func (b *Birc) handlePrivMsg(client *girc.Client, event girc.Event) {
 	b.Log.Debugf("<= Sending message from %s on %s to gateway", event.Params[0], b.Account)
 	if b.ActivityTimeout > 0 {
 		b.Log.Debugf("<= Updating last-active time for user %s", event.Source.Name)
-		b.activeUsers[event.Source.Name] = time.Now().Unix()
+		b.markUserActive(event.Source.Name, time.Now().Unix())
 	}
 	b.Remote <- rmsg
 	b.cleanActiveMap()
diff --git a/bridge/irc/irc.go b/bridge/irc/irc.go
index 886ad6a0..db4134fb 100644
--- a/bridge/irc/irc.go
+++ b/bridge/irc/irc.go
@@ -10,6 +10,7 @@ import (
 	"sort"
 	"strconv"
 	"strings"
+	"sync"
 	"time"
 
 	"github.com/42wim/matterbridge/bridge"
@@ -29,6 +30,7 @@ type Birc struct {
 	names                                     map[string][]string
 	activeUsers                               map[string]int64
 	activeUsersLastCleaned                    int64
+	activeUsersMutex                          sync.RWMutex
 	connected                                 chan error
 	Local                                     chan config.Message // local queue for flood control
 	FirstConnection, authDone                 bool
@@ -432,20 +434,24 @@ func (b *Birc) getTLSConfig() (*tls.Config, error) {
 	return tlsConfig, nil
 }
 
-func (b *Birc) isUserActive(nick string) bool {
+func (b *Birc) isUserActive(nick string) (bool, int64) {
 	b.Log.Debugf("checking activity for %s", nick)
 	if b.ActivityTimeout == 0 {
-		return true
-	} else if activeTime, ok := b.activeUsers[nick]; ok {
-		now := time.Now().Unix()
-		b.Log.Debugf("last activity for %s was %d, currently %d", nick, activeTime, now)
-		if now < activeTime {
-			b.Log.Errorf("User %s has active time in the future: %d", nick, activeTime)
-			return true // err on the side of caution
+		return true, 0
+	} else {
+		b.activeUsersMutex.RLock()
+		defer b.activeUsersMutex.RUnlock()
+		if activeTime, ok := b.activeUsers[nick]; ok {
+			now := time.Now().Unix()
+			b.Log.Debugf("last activity for %s was %d, currently %d", nick, activeTime, now)
+			if now < activeTime {
+				b.Log.Errorf("User %s has active time in the future: %d", nick, activeTime)
+				return true, now // err on the side of caution
+			}
+			return (now - activeTime) < b.ActivityTimeout, activeTime
 		}
-		return (now - activeTime) < b.ActivityTimeout
 	}
-	return false
+	return false, 0
 }
 
 func (b *Birc) getPseudoChannel() string {
@@ -463,6 +469,8 @@ func (b *Birc) cleanActiveMap() {
 	if b.ActivityTimeout == 0 || (b.activeUsersLastCleaned-now < b.ActivityTimeout) {
 		return
 	}
+	b.activeUsersMutex.Lock()
+	defer b.activeUsersMutex.Unlock()
 	for nick, activeTime := range b.activeUsers {
 		if now-activeTime > b.ActivityTimeout {
 			b.Log.Debugf("last activity for %s was %d, currently %d. Deleting.", nick, activeTime, now)
@@ -470,3 +478,9 @@ func (b *Birc) cleanActiveMap() {
 		}
 	}
 }
+
+func (b *Birc) markUserActive(nick string, activeTime int64) {
+	b.activeUsersMutex.Lock()
+	defer b.activeUsersMutex.Unlock()
+	b.activeUsers[nick] = activeTime
+}