diff --git a/app/assets/javascripts/discourse/lib/utilities.js.es6 b/app/assets/javascripts/discourse/lib/utilities.js.es6
index b1b124518bc..a46fdb0c8c6 100644
--- a/app/assets/javascripts/discourse/lib/utilities.js.es6
+++ b/app/assets/javascripts/discourse/lib/utilities.js.es6
@@ -267,12 +267,12 @@ export function isAnImage(path) {
 
 export function allowsImages() {
   return authorizesAllExtensions() ||
-    (/(png|jpe?g|gif|bmp|tiff?|svg|webp|ico)/i).test(authorizedExtensions());
+    (/\.(png|jpe?g|gif|bmp|tiff?|svg|webp|ico)/i).test(authorizedExtensions());
 }
 
 export function allowsAttachments() {
   return authorizesAllExtensions() ||
-    !(/((png|jpe?g|gif|bmp|tiff?|svg|web|ico)(,\s)?)+$/i).test(authorizedExtensions());
+    !/^(\.(png|jpe?g|gif|bmp|tiff?|svg|webp|ico)(,\s)?)+$/i.test(authorizedExtensions());
 }
 
 export function displayErrorForUpload(data) {
diff --git a/test/javascripts/lib/utilities-test.js.es6 b/test/javascripts/lib/utilities-test.js.es6
index 59281334fc4..fd3583de8c0 100644
--- a/test/javascripts/lib/utilities-test.js.es6
+++ b/test/javascripts/lib/utilities-test.js.es6
@@ -164,13 +164,13 @@ test("avatarImg", function() {
 });
 
 test("allowsAttachments", function() {
-  Discourse.SiteSettings.authorized_extensions = "jpg|jpeg|gif";
+  Discourse.SiteSettings.authorized_extensions = ".jpg, .jpeg, .gif";
   not(allowsAttachments(), "no attachments allowed by default");
 
-  Discourse.SiteSettings.authorized_extensions = "jpg|jpeg|gif|*";
+  Discourse.SiteSettings.authorized_extensions = ".jpg, .jpeg, .gif, *";
   ok(allowsAttachments(), "attachments are allowed when all extensions are allowed");
 
-  Discourse.SiteSettings.authorized_extensions = "jpg|jpeg|gif|pdf";
+  Discourse.SiteSettings.authorized_extensions = ".jpg, .jpeg, .gif, .pdf";
   ok(allowsAttachments(), "attachments are allowed when at least one extension is not an image extension");
 });