diff --git a/modules/templates/util_avatar.go b/modules/templates/util_avatar.go
index 462668588a31..85832cf264cd 100644
--- a/modules/templates/util_avatar.go
+++ b/modules/templates/util_avatar.go
@@ -59,7 +59,7 @@ func (au *AvatarUtils) Avatar(item any, others ...any) template.HTML {
 		}
 	}
 
-	return ""
+	return AvatarHTML(avatars.DefaultAvatarLink(), size, class, "")
 }
 
 // AvatarByAction renders user avatars from action. args: action, size (int), class (string)
diff --git a/templates/repo/diff/comments.tmpl b/templates/repo/diff/comments.tmpl
index 1e9af5c4a1f6..2fbfe2fd6a07 100644
--- a/templates/repo/diff/comments.tmpl
+++ b/templates/repo/diff/comments.tmpl
@@ -3,7 +3,7 @@
 {{$createdStr:= TimeSinceUnix .CreatedUnix ctx.Locale}}
 <div class="comment" id="{{.HashTag}}">
 	{{if .OriginalAuthor}}
-		<span class="avatar"><img src="{{AppSubUrl}}/assets/img/avatar_default.png"></span>
+		<span class="avatar">{{ctx.AvatarUtils.Avatar nil}}</span>
 	{{else}}
 		{{template "shared/user/avatarlink" dict "user" .Poster}}
 	{{end}}
diff --git a/templates/repo/issue/view_content.tmpl b/templates/repo/issue/view_content.tmpl
index 9967997b9241..ed444f6dcee4 100644
--- a/templates/repo/issue/view_content.tmpl
+++ b/templates/repo/issue/view_content.tmpl
@@ -12,7 +12,7 @@
 			<div id="{{.Issue.HashTag}}" class="timeline-item comment first">
 				{{if .Issue.OriginalAuthor}}
 				<span class="timeline-avatar">
-					<img src="{{AppSubUrl}}/assets/img/avatar_default.png" width="40" height="40">
+					{{ctx.AvatarUtils.Avatar nil 40}}
 				</span>
 				{{else}}
 				<a class="timeline-avatar" {{if gt .Issue.Poster.ID 0}}href="{{.Issue.Poster.HomeLink}}"{{end}}>
diff --git a/templates/repo/issue/view_content/comments.tmpl b/templates/repo/issue/view_content/comments.tmpl
index ad7b836e9c9f..ade0ea34cfa4 100644
--- a/templates/repo/issue/view_content/comments.tmpl
+++ b/templates/repo/issue/view_content/comments.tmpl
@@ -17,7 +17,7 @@
 			<div class="timeline-item comment" id="{{.HashTag}}">
 			{{if .OriginalAuthor}}
 				<span class="timeline-avatar">
-					<img src="{{AppSubUrl}}/assets/img/avatar_default.png" width="40" height="40">
+					{{ctx.AvatarUtils.Avatar nil 40}}
 				</span>
 			{{else}}
 				<a class="timeline-avatar"{{if gt .Poster.ID 0}} href="{{.Poster.HomeLink}}"{{end}}>