diff --git a/lib/types/symbol/index.js b/lib/types/symbol/index.js
index 2a04feab8..df218cf19 100644
--- a/lib/types/symbol/index.js
+++ b/lib/types/symbol/index.js
@@ -2,6 +2,8 @@
 
 // Load modules
 
+const Util = require('util');
+
 const Any = require('../any');
 const Hoek = require('hoek');
 
@@ -20,13 +22,7 @@ internals.Map = class extends Map {
 
     toString() {
 
-        const entries = [...this].map(([key, symbol]) => {
-
-            key = typeof key === 'symbol' ? key.toString() : JSON.stringify(key);
-            return `${key} => ${symbol.toString()}`;
-        });
-
-        return `Map { ${entries.join(', ')} }`;
+        return Util.inspect(this);
     }
 };
 
@@ -76,7 +72,7 @@ internals.Symbol = class extends Any {
             Hoek.assert(entry && entry[Symbol.iterator], 'Entry must be an iterable');
             const [key, value] = entry;
 
-            Hoek.assert(typeof key !== 'object' && typeof key !== 'function', 'Key must be a simple type');
+            Hoek.assert(typeof key !== 'object' && typeof key !== 'function' && typeof key !== 'symbol', 'Key must not be an object, function, or Symbol');
             Hoek.assert(typeof value === 'symbol', 'Value must be a Symbol');
             obj._inner.map.set(key, value);
             symbols.push(value);
@@ -87,7 +83,7 @@ internals.Symbol = class extends Any {
 
     describe() {
 
-        const description = Any.prototype.describe.call(this);
+        const description = super.describe();
         description.map = new Map(this._inner.map);
         return description;
     }
diff --git a/test/types/symbol.js b/test/types/symbol.js
index 72ed7af31..450340c50 100644
--- a/test/types/symbol.js
+++ b/test/types/symbol.js
@@ -77,17 +77,17 @@ describe('symbol', () => {
 
             it('converts keys to correct symbol', () => {
 
-                const symbols = [Symbol(1), Symbol(2), Symbol(3)];
+                const symbols = [Symbol(1), Symbol(2)];
                 const otherSymbol = Symbol(1);
-                const map = new Map([[1, symbols[0]], ['two', symbols[1]], [symbols[0], symbols[2]]]);
+                const map = new Map([[1, symbols[0]], ['two', symbols[1]]]);
                 const rule = Joi.symbol().map(map);
                 Helper.validate(rule, [
                     [1, true, null, symbols[0]],
                     [symbols[0], true, null, symbols[0]],
                     ['1', false, null, {
-                        message: '"value" must be one of Map { 1 => Symbol(1), "two" => Symbol(2), Symbol(1) => Symbol(3) }',
+                        message: `"value" must be one of Map { 1 => Symbol(1), 'two' => Symbol(2) }`,
                         details: [{
-                            message: '"value" must be one of Map { 1 => Symbol(1), "two" => Symbol(2), Symbol(1) => Symbol(3) }',
+                            message: `"value" must be one of Map { 1 => Symbol(1), 'two' => Symbol(2) }`,
                             path: [],
                             type: 'symbol.map',
                             context: { label: 'value', key: undefined, map }
@@ -95,9 +95,9 @@ describe('symbol', () => {
                     }],
                     ['two', true, null, symbols[1]],
                     [otherSymbol, false, null, {
-                        message: '"value" must be one of [Symbol(1), Symbol(2), Symbol(3)]',
+                        message: '"value" must be one of [Symbol(1), Symbol(2)]',
                         details: [{
-                            message: '"value" must be one of [Symbol(1), Symbol(2), Symbol(3)]',
+                            message: '"value" must be one of [Symbol(1), Symbol(2)]',
                             path: [],
                             type: 'any.allowOnly',
                             context: { value: otherSymbol, label: 'value', valids: symbols, key: undefined }
@@ -125,9 +125,9 @@ describe('symbol', () => {
                         }]
                     }],
                     ['toString', false, null, {
-                        message: '"value" must be one of Map { "one" => Symbol(one), "two" => Symbol(two) }',
+                        message: `"value" must be one of Map { 'one' => Symbol(one), 'two' => Symbol(two) }`,
                         details: [{
-                            message: '"value" must be one of Map { "one" => Symbol(one), "two" => Symbol(two) }',
+                            message: `"value" must be one of Map { 'one' => Symbol(one), 'two' => Symbol(two) }`,
                             path: [],
                             type: 'symbol.map',
                             context: { label: 'value', key: undefined, map: new Map([['one', symbols[0]], ['two', symbols[1]]]) }
@@ -180,7 +180,15 @@ describe('symbol', () => {
 
                 expect(
                     () => Joi.symbol().map([[{}, Symbol()]])
-                ).to.throw('Key must be a simple type');
+                ).to.throw('Key must not be an object, function, or Symbol');
+
+                expect(
+                    () => Joi.symbol().map([[() => {}, Symbol()]])
+                ).to.throw('Key must not be an object, function, or Symbol');
+
+                expect(
+                    () => Joi.symbol().map([[Symbol(), Symbol()]])
+                ).to.throw('Key must not be an object, function, or Symbol');
             });
         });