diff --git a/modules/templates/helper.go b/modules/templates/helper.go
index 537ef71ccf..ad39baecb9 100644
--- a/modules/templates/helper.go
+++ b/modules/templates/helper.go
@@ -454,6 +454,7 @@ func NewFuncMap() []template.FuncMap {
 			}
 			return items
 		},
+		"HasPrefix": strings.HasPrefix,
 	}}
 }
 
diff --git a/templates/repo/header.tmpl b/templates/repo/header.tmpl
index 94ae5ed7e2..a2f31fc950 100644
--- a/templates/repo/header.tmpl
+++ b/templates/repo/header.tmpl
@@ -206,7 +206,7 @@
 				{{end}}
 
 				{{if or (.Permission.CanRead $.UnitTypeWiki) (.Permission.CanRead $.UnitTypeExternalWiki)}}
-					<a class="{{if .PageIsWiki}}active{{end}} item" href="{{.RepoLink}}/wiki" {{if (.Permission.CanRead $.UnitTypeExternalWiki)}} target="_blank" rel="noopener noreferrer" {{end}}>
+					<a class="{{if .PageIsWiki}}active{{end}} item" href="{{.RepoLink}}/wiki" {{if and (.Permission.CanRead $.UnitTypeExternalWiki) (not (HasPrefix ((.Repository.MustGetUnit $.UnitTypeExternalWiki).ExternalWikiConfig.ExternalWikiURL) (.Repository.HTMLURL)))}} target="_blank" rel="noopener noreferrer" {{end}}>
 						{{svg "octicon-book"}} {{.i18n.Tr "repo.wiki"}}
 					</a>
 				{{end}}