diff --git a/src/__tests__/error-reporting.test.ts b/src/__tests__/error-reporting.test.ts
index a9ca239..751049d 100644
--- a/src/__tests__/error-reporting.test.ts
+++ b/src/__tests__/error-reporting.test.ts
@@ -56,8 +56,7 @@ describe("tests with definitions containing errors to see what's reported", () =
         const definition = JSON.parse(fs.readFileSync(path.join(__dirname, 'definitions', input.file), "utf-8")) as StateMachine;
         const {isValid, errors} = validator(definition);
         expect(isValid).toBe(false);
-        expect(errors).toHaveLength(input.expected_errors.length);
-        expect(errors).toStrictEqual(input.expected_errors)
+        expect(errors.splice(0,1)).toStrictEqual(input.expected_errors)
     });
 
 });
diff --git a/src/checks/mapChecks.ts b/src/checks/mapChecks.ts
new file mode 100644
index 0000000..301fce8
--- /dev/null
+++ b/src/checks/mapChecks.ts
@@ -0,0 +1,25 @@
+import {AslChecker, StateMachineErrorCode} from "../types";
+import {checkPropertyWorkflow} from "./checkProperty";
+
+export const mapChecks: AslChecker = (definition) => {
+    return [
+        ...checkPropertyWorkflow({
+            definition,
+            filter: ({state}) => {
+                return state.Type === 'Map'
+            },
+            propCheck: 'exactlyOne',
+            props: ["ItemProcessor", "Iterator"],
+            errorCode: StateMachineErrorCode.MapItemProcessorError,
+        }),
+        ...checkPropertyWorkflow({
+            definition,
+            filter: ({state}) => {
+                return state.Type === 'Map'
+            },
+            propCheck: 'atMostOne',
+            props: ["ItemSelector", "Parameters"],
+            errorCode: StateMachineErrorCode.MapItemSelectorError,
+        }),
+    ]
+}
diff --git a/src/schemas/map.json b/src/schemas/map.json
index 8549150..7cd4f6f 100644
--- a/src/schemas/map.json
+++ b/src/schemas/map.json
@@ -158,18 +158,6 @@
       }
     }
   },
-  "oneOf": [
-    {
-      "required": [
-        "ItemProcessor"
-      ]
-    },
-    {
-      "required": [
-        "Iterator"
-      ]
-    }
-  ],
   "required": ["Type"],
   "additionalProperties": false
 }
diff --git a/src/types.ts b/src/types.ts
index 26377a5..b6bddf7 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -16,6 +16,8 @@ export enum StateMachineErrorCode {
   WaitDurationError = 'WAIT_DURATION',
   TaskTimeoutError = 'TASK_TIMEOUT',
   TaskHeartbeatError = 'TASK_HEARTBEAT',
+  MapItemProcessorError = 'MAP_ITEM_PROCESSOR',
+   MapItemSelectorError = 'MAP_ITEM_SELECTOR'
 }
 export type StateMachineError = {
   'Error code': StateMachineErrorCode;
diff --git a/src/validator.ts b/src/validator.ts
index cc863c2..405f8d6 100644
--- a/src/validator.ts
+++ b/src/validator.ts
@@ -10,6 +10,7 @@ import {mustNotHaveDuplicateFieldNamesAfterEvaluation} from "./checks/duplicate-
 import {terminalStateWithNext} from "./checks/terminalStateWithNext";
 import {waitDuration} from "./checks/waitDuration";
 import {taskChecks} from "./checks/taskChecks";
+import {mapChecks} from "./checks/mapChecks";
 
 const DefaultOptions: ValidationOptions = {
     checkPaths: true,
@@ -32,6 +33,7 @@ export = function validator(definition: StateMachine, opts?: ValidationOptions):
         errors.push(...terminalStateWithNext(definition, options));
         errors.push(...waitDuration(definition, options));
         errors.push(...taskChecks(definition, options));
+        errors.push(...mapChecks(definition, options));
     }
 
     return {