diff --git a/raml/schemas/definitions/avatars.json b/raml/schemas/definitions/avatars.json
index e030dee7ba3ae5d40813f92d10d6871b9b30b1b0..c17549878676559b1370b59c4c3abc3142456d85 100644
--- a/raml/schemas/definitions/avatars.json
+++ b/raml/schemas/definitions/avatars.json
@@ -3,7 +3,10 @@
   "title": "Group",
   "type": "object",
   "properties": {
-    "gravatar":         {"type": ["string", "null"], "format": "uri" },
+    "gravatar":         {
+      "type": ["string", "null"],
+      "pattern": "^https:",
+      "format": "uri" },
     "provider":         {"type": ["string", "null"], "format": "uri" },
     "custom":           {"type": ["string", "null"], "format": "uri" }
   },