diff --git a/.gitignore b/.gitignore
index c86af6f..fa1d02a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -5,6 +5,7 @@
 /node_modules
 
 /.php_cs.cache
+/.php-cs-fixer.cache
 /.phpunit.result.cache
 
 php-cs-fixer.phar
diff --git a/.php_cs.dist b/.php-cs-fixer.dist.php
similarity index 92%
rename from .php_cs.dist
rename to .php-cs-fixer.dist.php
index 704f437..3594ae9 100644
--- a/.php_cs.dist
+++ b/.php-cs-fixer.dist.php
@@ -1,6 +1,6 @@
 <?php
 
-return PhpCsFixer\Config::create()
+return (new PhpCsFixer\Config())
     ->setRules([
         '@PSR2' => true,
         'array_syntax' => ['syntax' => 'short'],
diff --git a/Makefile b/Makefile
index ee99b2a..b4fae49 100644
--- a/Makefile
+++ b/Makefile
@@ -34,7 +34,7 @@ check-style: php-cs-fixer.phar
 
 fix-style: php-cs-fixer.phar
 	$(DOCKER_PHP) vendor/bin/indent --tabs composer.json
-	$(DOCKER_PHP) vendor/bin/indent --spaces .php_cs.dist
+	$(DOCKER_PHP) vendor/bin/indent --spaces .php-cs-fixer.dist.php
 	$(DOCKER_PHP) ./php-cs-fixer.phar fix src/ --diff
 
 install: composer.lock yarn.lock
diff --git a/src/json/JsonPointer.php b/src/json/JsonPointer.php
index 0e1f75e..3121e08 100644
--- a/src/json/JsonPointer.php
+++ b/src/json/JsonPointer.php
@@ -107,11 +107,11 @@ public function evaluate($jsonDocument)
 
         foreach ($this->getPath() as $part) {
             if (is_array($currentReference)) {
-//                if (!preg_match('~^([1-9]*[0-9]|-)$~', $part)) {
-//                    throw new NonexistentJsonPointerReferenceException(
-//                        "Failed to evaluate pointer '$this->_pointer'. Invalid pointer path '$part' for Array at path '$currentPath'."
-//                    );
-//                }
+                //                if (!preg_match('~^([1-9]*[0-9]|-)$~', $part)) {
+                //                    throw new NonexistentJsonPointerReferenceException(
+                //                        "Failed to evaluate pointer '$this->_pointer'. Invalid pointer path '$part' for Array at path '$currentPath'."
+                //                    );
+                //                }
                 if ($part === '-' || !array_key_exists($part, $currentReference)) {
                     throw new NonexistentJsonPointerReferenceException(
                         "Failed to evaluate pointer '$this->_pointer'. Array has no member $part at path '$currentPath'."
diff --git a/src/spec/Paths.php b/src/spec/Paths.php
index e504a90..7257bd7 100644
--- a/src/spec/Paths.php
+++ b/src/spec/Paths.php
@@ -46,6 +46,10 @@ class Paths implements SpecObjectInterface, DocumentContextInterface, ArrayAcces
      * @var JsonPointer|null
      */
     private $_jsonPointer;
+    /**
+     * @var string
+     */
+    private $_operationsIds = [];
 
 
     /**
@@ -147,6 +151,18 @@ public function validate(): bool
             if (strpos($key, '/') !== 0) {
                 $this->_errors[] = "Path must begin with /: $key";
             }
+            $operations = $path->getOperations();
+            foreach($operations as $operation) {
+                $id = $operation->operationId;
+                if(empty($id)) {
+                    continue;
+                }
+                if(!empty($this->_operationsIds[$id]) && $this->_operationsIds[$id]) {
+                    $this->_errors[] = "Operation ID '$id', already exist. Operation IDs must be unique.";
+                    $valid = false;
+                }
+                $this->_operationsIds[$id] = true;
+            }
         }
         return $valid && empty($this->_errors);
     }
diff --git a/tests/ReaderTest.php b/tests/ReaderTest.php
index 589b7cb..218e504 100644
--- a/tests/ReaderTest.php
+++ b/tests/ReaderTest.php
@@ -129,6 +129,241 @@ public function testSymfonyYamlBugHunt()
     }
 
 
+    public function testForceUniqueOperationIdJSON(){
+      //Duplicate
+      $api = \cebe\openapi\Reader::readFromJson(<<<JSON
+      {
+        "openapi": "3.0.0",
+        "info": {
+          "title": "Test API",
+          "version": "1.0.0"
+        },
+        "paths": {
+          "/path": {
+            "get": {
+              "operationId": "op1",
+              "responses": {
+                "200": {
+                  "description": "Success"
+                }
+              }
+            },
+            "post": {
+              "operationId": "op1",
+              "responses": {
+                "200": {
+                  "description": "Success"
+                }
+              }
+            }
+          }
+        }
+      }
+      JSON);
+      
+      $this->assertFalse($api->validate());   
+      
+      //Non duplicate
+      $api = \cebe\openapi\Reader::readFromJson(<<<JSON
+      {
+        "openapi": "3.0.0",
+        "info": {
+          "title": "Test API",
+          "version": "1.0.0"
+        },
+        "paths": {
+          "/path": {
+            "get": {
+              "operationId": "op1",
+              "responses": {
+                "200": {
+                  "description": "Success"
+                }
+              }
+            },
+            "post": {
+              "operationId": "op2",
+              "responses": {
+                "200": {
+                  "description": "Success"
+                }
+              }
+            }
+          }
+        }
+      }
+      JSON);
+      
+      $this->assertTrue($api->validate());        
+    }
+
+    //Different Paths
+    public function testForceUniqueOperationIdInDifferentPathsJSON(){
+      //Duplicate
+      $api = \cebe\openapi\Reader::readFromJson(<<<JSON
+      {
+        "openapi": "3.0.0",
+        "info": {
+          "title": "Test API",
+          "version": "1.0.0"
+        },
+        "paths": {
+          "/path1": {
+            "get": {
+              "operationId": "op1",
+              "responses": {
+                "200": {
+                  "description": "Success"
+                }
+              }
+            }
+          },
+          "/path2": {
+            "get": {
+              "operationId": "op1",
+              "responses": {
+                "200": {
+                  "description": "Success"
+                }
+              }
+            }
+          }
+        }
+      }
+      JSON);
+      
+      $this->assertFalse($api->validate());   
+      
+      // Non duplicate
+      $api = \cebe\openapi\Reader::readFromJson(<<<JSON
+      {
+        "openapi": "3.0.0",
+        "info": {
+          "title": "Test API",
+          "version": "1.0.0"
+        },
+        "paths": {
+          "/path1": {
+            "get": {
+              "operationId": "op1",
+              "responses": {
+                "200": {
+                  "description": "Success"
+                }
+              }
+            }
+          },
+          "/path2": {
+            "post": {
+              "operationId": "op2",
+              "responses": {
+                "200": {
+                  "description": "Success"
+                }
+              }
+            }
+          }
+        }
+      }
+      JSON);
+      
+      // $this->assertTrue($api->validate());        
+    }
+
+    //The same paths
+    public function testForceUniqueOperationIdYAML(){
+      //Duplicate
+      $openapi = \cebe\openapi\Reader::readFromYaml(<<<YAML
+      openapi: 3.0.0
+      info:
+        title: "Test API"
+        version: "1.0.0"
+      paths:
+        /path:      
+          get:
+            operationId: op1
+            responses:
+              '200':
+                description: Validation error
+          post:
+            operationId: op1
+            responses:
+              '200':
+                description: Validation error
+      YAML);
+      $this->assertFalse($openapi->validate());  
+      
+      //Non Duplicate
+      $openapi = \cebe\openapi\Reader::readFromYaml(<<<YAML
+      openapi: 3.0.0
+      info:
+        title: "Test API"
+        version: "1.0.0"
+      paths:
+        /path:      
+          get:
+            operationId: op1
+            responses:
+              '200':
+                description: Validation error
+          post:
+            operationId: op2
+            responses:
+              '200':
+                description: Validation error
+      YAML);
+      $this->assertTrue($openapi->validate()); 
+    }
+
+    //Duplicate Different paths
+    public function testForceUniqueOperationIdInDifferentPathsYAML(){
+      //Duplicate
+      $openapi = \cebe\openapi\Reader::readFromYaml(<<<YAML
+      openapi: 3.0.0
+      info:
+        title: "Test API"
+        version: "1.0.0"
+      paths:
+        /path1:      
+          get:
+            operationId: op1
+            responses:
+              '200':
+                description: Validation error
+        /path2:      
+          get:
+            operationId: op1
+            responses:
+              '200':
+                description: Validation error                
+
+      YAML);
+      $this->assertFalse($openapi->validate());  
+      
+      //Non Duplicate
+      $openapi = \cebe\openapi\Reader::readFromYaml(<<<YAML
+      openapi: 3.0.0
+      info:
+        title: "Test API"
+        version: "1.0.0"
+      paths:
+        /path1:      
+          get:
+            operationId: op1
+            responses:
+              '200':
+                description: Validation error
+        /path2:      
+          get:
+            operationId: op2
+            responses:
+              '200':
+                description: Validation error   
+      YAML);
+      $this->assertTrue($openapi->validate()); 
+    }    
+
+
     // TODO test invalid JSON
     // TODO test invalid YAML
 }