diff --git a/pkg/modules/avatar/initials/initials.go b/pkg/modules/avatar/initials/initials.go
index 55676cb6b..8ef07cf98 100644
--- a/pkg/modules/avatar/initials/initials.go
+++ b/pkg/modules/avatar/initials/initials.go
@@ -22,6 +22,7 @@ import (
 	"github.com/disintegration/imaging"
 	"strconv"
 	"strings"
+	"sync"
 
 	"bytes"
 	"github.com/golang/freetype/truetype"
@@ -51,8 +52,10 @@ var (
 	}
 
 	// Contain the created avatars with a size of defaultSize
-	cache        = map[int64]*image.RGBA64{}
-	cacheResized = map[string][]byte{}
+	cache            = map[int64]*image.RGBA64{}
+	cacheLock        = sync.Mutex{}
+	cacheResized     = map[string][]byte{}
+	cacheResizedLock = sync.Mutex{}
 )
 
 func init() {
@@ -132,7 +135,9 @@ func getAvatarForUser(u *user.User) (fullSizeAvatar *image.RGBA64, err error) {
 		if err != nil {
 			return nil, err
 		}
+		cacheLock.Lock()
 		cache[u.ID] = fullSizeAvatar
+		cacheLock.Unlock()
 	}
 
 	return fullSizeAvatar, err
@@ -157,7 +162,9 @@ func (p *Provider) GetAvatar(u *user.User, size int64) (avatar []byte, mimeType
 			return nil, "", err
 		}
 		avatar = buf.Bytes()
+		cacheResizedLock.Lock()
 		cacheResized[cacheKey] = avatar
+		cacheResizedLock.Unlock()
 	} else {
 		log.Debugf("Serving initials avatar for user %d and size %d from cache", u.ID, size)
 	}