diff --git a/README.md b/README.md
index 36d9eca926..cd7f19e4fa 100644
--- a/README.md
+++ b/README.md
@@ -149,6 +149,69 @@ The file format is described in [canonical-schema.json](./canonical-schema.json)
   ]
 }
 ```
+### Test Data Format for Tests with Timeout constraints
+
+This example shows the possible use of the optional timeout constraint for a test, not all tests need a timeout and the timeout can vary from test to test:
+```json
+{
+  "exercise": "alphametics",
+  "cases": [
+    {
+      "uuid": "e0c08b07-9028-4d5f-91e1-d178fead8e1a",
+      "description": "puzzle with three letters",
+      "property": "solve",
+      "input": {
+        "puzzle": "I + BB == ILL"
+      },
+      "expected": {
+        "I": 1,
+        "B": 9,
+        "L": 0
+      }
+    },
+    {
+      "uuid": "12125a75-7284-4f9a-a5fa-191471e0d44f",
+      "description": "puzzle with eight letters",
+      "property": "solve",
+      "input": {
+        "puzzle": "SEND + MORE == MONEY"
+      },
+      "expected": {
+        "S": 9,
+        "E": 5,
+        "N": 6,
+        "D": 7,
+        "M": 1,
+        "O": 0,
+        "R": 8,
+        "Y": 2
+      },
+      "timeout": 2000      
+    },
+    {
+      "uuid": "fb05955f-38dc-477a-a0b6-5ef78969fffa",
+      "description": "puzzle with ten letters",
+      "property": "solve",
+      "input": {
+        "puzzle": "AND + A + STRONG + OFFENSE + AS + A + GOOD == DEFENSE"
+      },
+      "expected": {
+        "A": 5,
+        "D": 3,
+        "E": 4,
+        "F": 7,
+        "G": 8,
+        "N": 0,
+        "O": 2,
+        "R": 1,
+        "S": 6,
+        "T": 9
+      },
+      "timeout": 5000
+    }
+  ]
+}
+```
 
 ## Scenarios
 
diff --git a/canonical-schema.json b/canonical-schema.json
index 91441e625a..41b7148fc7 100644
--- a/canonical-schema.json
+++ b/canonical-schema.json
@@ -86,6 +86,7 @@
                 , "property"    : { "$ref": "#/definitions/property"    }
                 , "input"       : { "$ref": "#/definitions/input"       }
                 , "expected"    : { "$ref": "#/definitions/expected"    }
+                , "timeout"     : { "$ref": "#/definitions/timeout"     }
                 }
           , "additionalProperties": false
           },
@@ -156,6 +157,11 @@
                }
           },
 
+     "timeout":
+          { "description": "Test timeout in milliseconds"
+          , "type"       : "integer"
+          },
+
       "error":
           { "description": "A message describing an error condition"
           , "type"       : "string"