diff --git a/webapp/questionSchema.json b/webapp/questionSchema.json
index 06a4f64..37bef74 100644
--- a/webapp/questionSchema.json
+++ b/webapp/questionSchema.json
@@ -110,10 +110,36 @@
                 "options": {
                     "properties": {
                         "enum": {
-                            "items": {
-                                "type": "string"
-                            },
-                            "type": "array"
+                            "anyOf": [
+                                {
+                                    "maxItems": 0,
+                                    "minItems": 0,
+                                    "type": "array"
+                                },
+                                {
+                                    "items": [
+                                        {
+                                            "type": "number"
+                                        }
+                                    ],
+                                    "maxItems": 1,
+                                    "minItems": 1,
+                                    "type": "array"
+                                },
+                                {
+                                    "items": [
+                                        {
+                                            "type": "number"
+                                        },
+                                        {
+                                            "type": "number"
+                                        }
+                                    ],
+                                    "maxItems": 2,
+                                    "minItems": 2,
+                                    "type": "array"
+                                }
+                            ]
                         }
                     },
                     "type": "object"