diff --git a/README.md b/README.md
index 20fee54..971b6eb 100755
--- a/README.md
+++ b/README.md
@@ -48,6 +48,8 @@ Iodine.isInteger(item_1); // true
 Iodine.isInteger(item_2); // false
 ```
 
+Single checks return a `true` or `false` value, indicating whether the item passed validation.
+
 ## Multiple checks
 
 If you want to verify whether an item passes a set of rules, you should use the main `is` method. This method accepts two parameters. The first, is the item you want to check. The second, is an array of rules that should be run in sequence e.g.
@@ -57,30 +59,40 @@ let item_1 = 7;
 let item_2 = 'string';
 
 Iodine.is(item_1, ['required', 'integer']); // true
-Iodine.is(item_2, ['required', 'integer']); // false
+Iodine.is(item_2, ['required', 'integer']); // string - 'integer'
 ```
 
 The `is` method will return `true` if the item passes every rule.
 
-Alternatively, the name of the first rule that failed will be returned e.g. `'integer'`.
+If the item fails to validate, the first rule that it failed to satisfy will be returned e.g. `'integer'`.
 
 > Version 1 of Iodine only returned the rule name e.g. 'minimum'. Version 2+ returns the rule name and any supplied parameter e.g. 'minimum:7'.
 
 ## Additional parameters
 
-Some rules require extra parameters. You can supply them by adding them to the rule with a semicolon separator e.g.
+Some rules require extra parameters e.g.
 
 ```js
 let item_1 = 7;
-let item_2 = 'string';
+let item_2 = 4;
+
+Iodine.isMinimum(item_1, 5); // true
+Iodine.isMinimum(item_2, 5); // false
+```
+
+For multiple checks, you can supply the parameters by appending them to the rule with a semicolon separator e.g.
+
+```js
+let item_1 = 7;
+let item_2 = 4;
 
-Iodine.is(item_1, ['required', 'integer', 'minimum:5', 'maximum:10']); // true
-Iodine.is(item_2, ['required', 'integer', 'minimum:5', 'maximum:10']); // false
+Iodine.is(item_1, ['required', 'integer', 'minimum:5']); // true
+Iodine.is(item_2, ['required', 'integer', 'minimum:5']); // string - 'minimum:5'
 ```
 
 ## Optional values
 
-Sometimes, you may wish to allow for optional values. Iodine supports this with the `optional` rule:
+When performing multiple checks, you may wish to allow for optional values. Iodine supports this with the `optional` rule:
 
 ```js
 let item_1 = 7;
@@ -89,7 +101,7 @@ let item_3 = 'string';
 
 Iodine.is(item_1, ['optional', 'integer']); // true
 Iodine.is(item_2, ['optional', 'integer']); // true
-Iodine.is(item_3, ['optional', 'integer']); // false
+Iodine.is(item_3, ['optional', 'integer']); // string - 'integer'
 ```
 
 **IMPORTANT**: If you wish to allow for optional values, then you must supply `'optional'` as the first rule in the list.
@@ -102,10 +114,10 @@ Iodine includes a default set of error messages for the English language. To ret
 Iodine.getErrorMessage('array'); // string
 ```
 
-When dealing with parameters, the `getErrorMessage` method allows you to supply the rule either as a single `string` or as two arguments (the rule and parameter) e.g.
+When dealing with rules that have parameters, the `getErrorMessage` method allows you to supply the rule either as a combined `string` or as two arguments (the rule and parameter) e.g.
 
 ```js
-Iodine.getErrorMessage('minimum:7'); // string
+Iodine.getErrorMessage('minimum:7');  // string
 Iodine.getErrorMessage('minimum', 7); // string
 ```
 
diff --git a/package.json b/package.json
index a828af0..43c4ab5 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
     "name": "@kingshott/iodine",
-    "version": "2.0.1",
+    "version": "2.0.2",
     "description": "A micro client-side validation library",
     "repository": {
         "type": "git",
diff --git a/resources/version.svg b/resources/version.svg
index 593c008..289526b 100644
--- a/resources/version.svg
+++ b/resources/version.svg
@@ -14,7 +14,7 @@
     <g fill="#fff" text-anchor="middle" font-family="DejaVu Sans,Verdana,Geneva,sans-serif" font-size="11">
         <text x="23.5" y="15" fill="#010101" fill-opacity=".3">stable</text>
         <text x="23.5" y="14">stable</text>
-        <text x="67.5" y="15" fill="#010101" fill-opacity=".3">v2.0.1</text>
-        <text x="67.5" y="14">v2.0.1</text>
+        <text x="67.5" y="15" fill="#010101" fill-opacity=".3">v2.0.2</text>
+        <text x="67.5" y="14">v2.0.2</text>
     </g>
 </svg>
\ No newline at end of file
diff --git a/src/iodine.js b/src/iodine.js
index ab50e17..c635e75 100644
--- a/src/iodine.js
+++ b/src/iodine.js
@@ -84,7 +84,7 @@ export default class Iodine
 	 * Retrieve an error message for the given rule.
 	 *
 	 **/
-	getErrorMessage(rule, arg = null)
+	getErrorMessage(rule, arg = undefined)
 	{
 		let key   = rule.split(':')[0];
 		let param = arg || rule.split(':')[1];
@@ -95,7 +95,7 @@ export default class Iodine
 			});
 		}
 
-		return param === undefined
+		return [null, undefined].includes(param)
 			 ? this.messages[key]
 			 : this.messages[key].replace("[PARAM]", param);
 	}
diff --git a/tests/test.js b/tests/test.js
index 0e0654e..a0c73b9 100644
--- a/tests/test.js
+++ b/tests/test.js
@@ -400,6 +400,7 @@ test('it validates values against multiple rules', () => {
 test('it retrieves formatted error messages for rules', () => {
 	let time = Date.UTC(2020, 4, 2, 3, 17, 0);
     expect(Iodine.getErrorMessage('array')).toBe('Field must be an array');
+    expect(Iodine.getErrorMessage('endingWith')).toBe(`Field must end with '[PARAM]'`);
     expect(Iodine.getErrorMessage('endingWith:world')).toBe(`Field must end with 'world'`);
     expect(Iodine.getErrorMessage('endingWith', 'world')).toBe(`Field must end with 'world'`);
     expect(Iodine.getErrorMessage(`after:${time}`)).toBe(`The date must be after: '2 May 2020, 04:17'`);