diff --git a/phpBB/adm/style/install_header.html b/phpBB/adm/style/install_header.html
index 5631b83e17..2db1b02c57 100644
--- a/phpBB/adm/style/install_header.html
+++ b/phpBB/adm/style/install_header.html
@@ -2,6 +2,7 @@
 <html dir="{S_CONTENT_DIRECTION}" lang="{S_USER_LANG}">
 <head>
 <meta charset="utf-8">
+<meta name="viewport" content="width=device-width" />
 <!-- IF META -->{META}<!-- ENDIF -->
 <title>{PAGE_TITLE}</title>
 
diff --git a/phpBB/adm/style/overall_header.html b/phpBB/adm/style/overall_header.html
index 3a9b6db2a3..b411671d59 100644
--- a/phpBB/adm/style/overall_header.html
+++ b/phpBB/adm/style/overall_header.html
@@ -2,6 +2,7 @@
 <html dir="{S_CONTENT_DIRECTION}" lang="{S_USER_LANG}">
 <head>
 <meta charset="utf-8">
+<meta name="viewport" content="width=device-width" />
 <!-- IF META -->{META}<!-- ENDIF -->
 <title>{PAGE_TITLE}</title>
 
