diff --git a/administrator/language/en-GB/en-GB.lib_joomla.ini b/administrator/language/en-GB/en-GB.lib_joomla.ini
index 5aa2d69e3ff5c..4b8ba81f03466 100644
--- a/administrator/language/en-GB/en-GB.lib_joomla.ini
+++ b/administrator/language/en-GB/en-GB.lib_joomla.ini
@@ -670,7 +670,8 @@ JLIB_MEDIA_ERROR_WARNFILETOOLARGE="This file is too large to upload."
 JLIB_MEDIA_ERROR_WARNFILETYPE="This file type is not supported."
 JLIB_MEDIA_ERROR_WARNIEXSS="Possible IE XSS Attack found."
 JLIB_MEDIA_ERROR_WARNINVALID_IMG="Not a valid image."
-JLIB_MEDIA_ERROR_WARNINVALID_MIME="Invalid mime type detected."
+; Do not sync the next line with the frontend! This is expected to be different from the frontend string.
+JLIB_MEDIA_ERROR_WARNINVALID_MIME="Unable to detect the mime type for this file. For security purposes this file has not been uploaded. Please contact your host and check that the mime_content_type or the fileinfo extension is enabled in PHP."
 JLIB_MEDIA_ERROR_WARNINVALID_MIMETYPE="Illegal mime type detected: %s"
 JLIB_MEDIA_ERROR_WARNNOTADMIN="Uploaded file is not an image file and you do not have permission."
 
diff --git a/language/en-GB/en-GB.lib_joomla.ini b/language/en-GB/en-GB.lib_joomla.ini
index 5aa2d69e3ff5c..998012f7ddc5b 100644
--- a/language/en-GB/en-GB.lib_joomla.ini
+++ b/language/en-GB/en-GB.lib_joomla.ini
@@ -670,7 +670,8 @@ JLIB_MEDIA_ERROR_WARNFILETOOLARGE="This file is too large to upload."
 JLIB_MEDIA_ERROR_WARNFILETYPE="This file type is not supported."
 JLIB_MEDIA_ERROR_WARNIEXSS="Possible IE XSS Attack found."
 JLIB_MEDIA_ERROR_WARNINVALID_IMG="Not a valid image."
-JLIB_MEDIA_ERROR_WARNINVALID_MIME="Invalid mime type detected."
+; Do not sync the next line with the backend! This is expected to be different from the backend string.
+JLIB_MEDIA_ERROR_WARNINVALID_MIME="Unable to upload this file."
 JLIB_MEDIA_ERROR_WARNINVALID_MIMETYPE="Illegal mime type detected: %s"
 JLIB_MEDIA_ERROR_WARNNOTADMIN="Uploaded file is not an image file and you do not have permission."