diff --git a/README.md b/README.md
index 67f2689..363ad11 100644
--- a/README.md
+++ b/README.md
@@ -186,6 +186,18 @@ console.log(braces.expand('a{b}c'));
 console.log(braces('a/{b,c}/d', { maxLength: 3 }));  //=> throws an error
 ```
 
+### options.maxSymbols
+
+**Type**: `Number`
+
+**Default**: `1024`
+
+**Description**: Limit the count of unique symbols the input string. 
+
+```js
+console.log(braces('a/{b,c}/d', { maxSymbols: 2 }));  //=> throws an error
+```
+
 ### options.expand
 
 **Type**: `Boolean`
diff --git a/lib/constants.js b/lib/constants.js
index a937943..3280bea 100644
--- a/lib/constants.js
+++ b/lib/constants.js
@@ -2,6 +2,7 @@
 
 module.exports = {
   MAX_LENGTH: 1024 * 64,
+  MAX_SYMBOLS: 1024,
 
   // Digits
   CHAR_0: '0', /* 0 */
diff --git a/lib/parse.js b/lib/parse.js
index 145ea26..7a724b8 100644
--- a/lib/parse.js
+++ b/lib/parse.js
@@ -1,6 +1,7 @@
 'use strict';
 
 const stringify = require('./stringify');
+const {isCorrectBraces, validateInput} = require('./validate-input');
 
 /**
  * Constants
@@ -8,6 +9,7 @@ const stringify = require('./stringify');
 
 const {
   MAX_LENGTH,
+  MAX_SYMBOLS,
   CHAR_BACKSLASH, /* \ */
   CHAR_BACKTICK, /* ` */
   CHAR_COMMA, /* , */
@@ -34,6 +36,11 @@ const parse = (input, options = {}) => {
   }
 
   let opts = options || {};
+
+  validateInput(input, {
+    maxSymbols: opts.maxSymbols || MAX_SYMBOLS,
+  });
+
   let max = typeof opts.maxLength === 'number' ? Math.min(MAX_LENGTH, opts.maxLength) : MAX_LENGTH;
   if (input.length > max) {
     throw new SyntaxError(`Input length (${input.length}), exceeds max characters (${max})`);
@@ -304,30 +311,43 @@ const parse = (input, options = {}) => {
     push({ type: 'text', value });
   }
 
+  flattenBlocks(stack)
+  markImbalancedBraces(ast);
+  push({ type: 'eos' });
+
+  return ast;
+};
+
+module.exports = parse;
+
+function markImbalancedBraces({nodes}) {
   // Mark imbalanced braces and brackets as invalid
+  for (const node of nodes) {
+    if (!node.nodes && !node.invalid) {
+      if (node.type === 'open') node.isOpen = true;
+      if (node.type === 'close') node.isClose = true;
+      if (!node.nodes) node.type = 'text';
+
+      node.invalid = true;
+    }
+
+    delete node.parent;
+    delete node.prev;
+  }
+}
+
+function flattenBlocks(stack) {
+  let block;
   do {
     block = stack.pop();
 
-    if (block.type !== 'root') {
-      block.nodes.forEach(node => {
-        if (!node.nodes) {
-          if (node.type === 'open') node.isOpen = true;
-          if (node.type === 'close') node.isClose = true;
-          if (!node.nodes) node.type = 'text';
-          node.invalid = true;
-        }
-      });
+    if (block.type === 'root')
+      continue;
 
-      // get the location of the block on parent.nodes (block's siblings)
-      let parent = stack[stack.length - 1];
-      let index = parent.nodes.indexOf(block);
-      // replace the (invalid) block with it's nodes
-      parent.nodes.splice(index, 1, ...block.nodes);
-    }
+    // get the location of the block on parent.nodes (block's siblings)
+    let parent = stack.at(-1);
+    let index = parent.nodes.indexOf(block);
+    // replace the (invalid) block with its nodes
+    parent.nodes.splice(index, 1, ...block.nodes);
   } while (stack.length > 0);
-
-  push({ type: 'eos' });
-  return ast;
-};
-
-module.exports = parse;
+}
diff --git a/lib/validate-input.js b/lib/validate-input.js
new file mode 100644
index 0000000..0f987b6
--- /dev/null
+++ b/lib/validate-input.js
@@ -0,0 +1,12 @@
+module.exports.validateInput = (line, {maxSymbols}) => {
+  const symbols = {};
+
+    for (const current of line) {
+        symbols[current] = (symbols[current] || 0) + 1;
+    }
+
+    for (const [value, count] of Object.entries(symbols)) {
+      if (count > maxSymbols)
+        throw SyntaxError(`To many symbols '${value}'. Maximum: ${maxSymbols} allowed. Received: ${count}`);
+    }
+};
diff --git a/test/braces.parse.js b/test/braces.parse.js
index b814558..09a2361 100644
--- a/test/braces.parse.js
+++ b/test/braces.parse.js
@@ -10,6 +10,16 @@ describe('braces.parse()', () => {
       let MAX_LENGTH = 1024 * 64;
       assert.throws(() => parse('.'.repeat(MAX_LENGTH + 2)));
     });
+    it('should throw an error when symbols exceeds max symbols count default', () => {
+      let SYMBOLS= 1024;
+      assert.throws(() => parse('.'.repeat(MAX_SYMBOLS * 2)));
+    });
+    it('should throw an error when symbols exceeds max symbols count ', () => {
+      let SYMBOLS= 2;
+      assert.throws(() => parse('...', {
+        maxSymbols: 2,
+      }));
+    });
   });
 
   describe('valid', () => {