diff --git a/cli.js b/cli.js
index 2615f721..f6f22a8f 100755
--- a/cli.js
+++ b/cli.js
@@ -37,9 +37,16 @@ if (!version) {
 
 try {
   const asyncapi = fs.readFileSync(asyncapiFile, 'utf-8');
-  console.log(converter.convert(asyncapi, version, {
+  let converted = converter.convert(asyncapi, version, {
     id: program.id,
-  }));
+  });
+
+  // JSON case
+  if (typeof converted === 'object') {
+    converted = JSON.stringify(converted, undefined, 2);
+  }
+
+  console.log(converted);
 } catch (e) {
   showErrorAndExit(e);
 }
diff --git a/lib/helpers.js b/lib/helpers.js
index 39e7028a..e4cb040e 100644
--- a/lib/helpers.js
+++ b/lib/helpers.js
@@ -3,16 +3,34 @@ const yaml = require('js-yaml');
 const helpers = module.exports;
 
 helpers.serialize = (text) => {
+    if (typeof text === 'object') {
+        return {
+            isYAML: false,
+            parsed: text,
+        };
+    }
+
     try {
+        const maybeJSON = JSON.parse(text);
+        if (typeof maybeJSON === 'object') {
+            return {
+                isYAML: false,
+                parsed: maybeJSON,
+            };
+        }
+
+        // if `maybeJSON` is object, then we have 100% sure that we operate on JSON, 
+        // but if it's `string` then we have option that it can be YAML but it doesn't have to be
         return {
             isYAML: true,
             parsed: yaml.safeLoad(text)
         };
     } catch (e) {
         try {
+            // try to parse again YAML, because the text itself may not have a JSON representation and cannot be represented as a JSON object/string
             return {
-                isYAML: false,
-                parsed: JSON.parse(text)
+                isYAML: true,
+                parsed: yaml.safeLoad(text)
             };
         } catch (err) {
             throw new Error('AsyncAPI document must be a valid JSON or YAML document.');
diff --git a/test/index.js b/test/index.js
index 62e9902c..62aaa456 100644
--- a/test/index.js
+++ b/test/index.js
@@ -2,6 +2,7 @@ const assert = require('assert');
 const fs = require('fs');
 const path = require("path");
 const { convert } = require('../lib');
+const { serialize } = require('../lib/helpers');
 
 describe('#convert', () => {
     it('should not convert to lowest version', () => {
@@ -193,6 +194,48 @@ describe('#convert', () => {
         const result = convert(input, '2.3.0');
         assertResults(output, result);
     });
+
+    it('should convert from 2.0.0 to 2.1.0 (JSON case)', () => {
+        const input = fs.readFileSync(path.resolve(__dirname, 'input', '2.0.0', 'streetlights.json'), 'utf8');
+        let output = fs.readFileSync(path.resolve(__dirname, 'output', '2.1.0', 'streetlights.json'), 'utf8');
+        let result = convert(input, '2.1.0');
+
+        output = JSON.stringify(JSON.parse(output));
+        result = JSON.stringify(JSON.parse(JSON.stringify(result)));
+        assert.strictEqual(output, result);
+    });
+});
+
+describe('#serialize', () => {
+    it('should serialize JSON', () => {
+        const input = '{"foo": "bar"}';
+        const output = serialize(input);
+        assert.strictEqual(output.isYAML, false);
+        assert.deepEqual(output.parsed, {foo: "bar"});
+    });
+
+    it('should serialize YAML', () => {
+        const input = 'foo: bar';
+        const output = serialize(input);
+        assert.strictEqual(output.isYAML, true);
+        assert.deepEqual(output.parsed, {foo: "bar"});
+    });
+
+    it('should serialize YAML (with JSON syntax)', () => {
+        const input = '{foo: bar}';
+        const output = serialize(input);
+        assert.strictEqual(output.isYAML, true);
+        assert.deepEqual(output.parsed, {foo: "bar"});
+    });
+
+    it('should throw error', () => {
+        const input = '%{foo: bar}';
+        try {
+            serialize(input);
+        } catch(e) {
+            assert.strictEqual(e.message, 'AsyncAPI document must be a valid JSON or YAML document.');
+        }
+    });
 });
 
 /*
@@ -205,4 +248,4 @@ function removeLineBreaks(str) {
 
 function assertResults(output, result){
     assert.strictEqual(removeLineBreaks(output), removeLineBreaks(result));
-}
\ No newline at end of file
+}
diff --git a/test/input/2.0.0/streetlights.json b/test/input/2.0.0/streetlights.json
new file mode 100644
index 00000000..b226ee7a
--- /dev/null
+++ b/test/input/2.0.0/streetlights.json
@@ -0,0 +1,172 @@
+{
+  "asyncapi": "2.0.0",
+  "info": {
+    "title": "Streetlights API",
+    "version": "1.0.0",
+    "description": "The Smartylighting Streetlights API allows you to remotely manage the city lights.\n\n### Check out its awesome features:\n\n* Turn a specific streetlight on/off 🌃\n* Dim a specific streetlight 😎\n* Receive real-time information about environmental lighting conditions 📈\n",
+    "license": {
+      "name": "Apache 2.0",
+      "url": "https://www.apache.org/licenses/LICENSE-2.0"
+    }
+  },
+  "servers": {
+    "default": {
+      "url": "api.streetlights.smartylighting.com:{port}",
+      "description": "Test broker",
+      "variables": {
+        "port": {
+          "description": "Secure connection (TLS) is available through port 8883.",
+          "default": "1883",
+          "enum": [
+            "1883",
+            "8883"
+          ]
+        }
+      },
+      "protocol": "mqtt",
+      "security": [
+        {
+          "apiKey": []
+        }
+      ]
+    }
+  },
+  "components": {
+    "messages": {
+      "lightMeasured": {
+        "summary": "Inform about environmental lighting conditions for a particular streetlight.",
+        "payload": {
+          "$ref": "#/components/schemas/lightMeasuredPayload"
+        }
+      },
+      "turnOnOff": {
+        "summary": "Command a particular streetlight to turn the lights on or off.",
+        "payload": {
+          "$ref": "#/components/schemas/turnOnOffPayload"
+        }
+      },
+      "dimLight": {
+        "summary": "Command a particular streetlight to dim the lights.",
+        "payload": {
+          "$ref": "#/components/schemas/dimLightPayload"
+        }
+      }
+    },
+    "schemas": {
+      "lightMeasuredPayload": {
+        "type": "object",
+        "properties": {
+          "lumens": {
+            "type": "integer",
+            "minimum": 0,
+            "description": "Light intensity measured in lumens."
+          },
+          "sentAt": {
+            "$ref": "#/components/schemas/sentAt"
+          }
+        }
+      },
+      "turnOnOffPayload": {
+        "type": "object",
+        "properties": {
+          "command": {
+            "type": "string",
+            "enum": [
+              "on",
+              "off"
+            ],
+            "description": "Whether to turn on or off the light."
+          },
+          "sentAt": {
+            "$ref": "#/components/schemas/sentAt"
+          }
+        }
+      },
+      "dimLightPayload": {
+        "type": "object",
+        "properties": {
+          "percentage": {
+            "type": "integer",
+            "description": "Percentage to which the light should be dimmed to.",
+            "minimum": 0,
+            "maximum": 100
+          },
+          "sentAt": {
+            "$ref": "#/components/schemas/sentAt"
+          }
+        }
+      },
+      "sentAt": {
+        "type": "string",
+        "format": "date-time",
+        "description": "Date and time when the message was sent."
+      }
+    },
+    "securitySchemes": {
+      "apiKey": {
+        "type": "apiKey",
+        "in": "user",
+        "description": "Provide your API key as the user and leave the password empty."
+      }
+    },
+    "parameters": {
+      "streetlightId": {
+        "name": "streetlightId",
+        "description": "The ID of the streetlight.",
+        "schema": {
+          "type": "string"
+        }
+      }
+    }
+  },
+  "channels": {
+    "smartylighting/streetlights/1/0/event/{streetlightId}/lighting/measured": {
+      "parameters": {
+        "streetlightId": {
+          "$ref": "#/components/parameters/streetlightId"
+        }
+      },
+      "publish": {
+        "message": {
+          "$ref": "#/components/messages/lightMeasured"
+        }
+      }
+    },
+    "smartylighting/streetlights/1/0/action/{streetlightId}/turn/on": {
+      "parameters": {
+        "streetlightId": {
+          "$ref": "#/components/parameters/streetlightId"
+        }
+      },
+      "subscribe": {
+        "message": {
+          "$ref": "#/components/messages/turnOnOff"
+        }
+      }
+    },
+    "smartylighting/streetlights/1/0/action/{streetlightId}/turn/off": {
+      "parameters": {
+        "streetlightId": {
+          "$ref": "#/components/parameters/streetlightId"
+        }
+      },
+      "subscribe": {
+        "message": {
+          "$ref": "#/components/messages/turnOnOff"
+        }
+      }
+    },
+    "smartylighting/streetlights/1/0/action/{streetlightId}/dim": {
+      "parameters": {
+        "streetlightId": {
+          "$ref": "#/components/parameters/streetlightId"
+        }
+      },
+      "subscribe": {
+        "message": {
+          "$ref": "#/components/messages/dimLight"
+        }
+      }
+    }
+  }
+}
\ No newline at end of file
diff --git a/test/output/2.1.0/streetlights.json b/test/output/2.1.0/streetlights.json
new file mode 100644
index 00000000..67516481
--- /dev/null
+++ b/test/output/2.1.0/streetlights.json
@@ -0,0 +1,172 @@
+{
+  "asyncapi": "2.1.0",
+  "info": {
+    "title": "Streetlights API",
+    "version": "1.0.0",
+    "description": "The Smartylighting Streetlights API allows you to remotely manage the city lights.\n\n### Check out its awesome features:\n\n* Turn a specific streetlight on/off 🌃\n* Dim a specific streetlight 😎\n* Receive real-time information about environmental lighting conditions 📈\n",
+    "license": {
+      "name": "Apache 2.0",
+      "url": "https://www.apache.org/licenses/LICENSE-2.0"
+    }
+  },
+  "servers": {
+    "default": {
+      "url": "api.streetlights.smartylighting.com:{port}",
+      "description": "Test broker",
+      "variables": {
+        "port": {
+          "description": "Secure connection (TLS) is available through port 8883.",
+          "default": "1883",
+          "enum": [
+            "1883",
+            "8883"
+          ]
+        }
+      },
+      "protocol": "mqtt",
+      "security": [
+        {
+          "apiKey": []
+        }
+      ]
+    }
+  },
+  "components": {
+    "messages": {
+      "lightMeasured": {
+        "summary": "Inform about environmental lighting conditions for a particular streetlight.",
+        "payload": {
+          "$ref": "#/components/schemas/lightMeasuredPayload"
+        }
+      },
+      "turnOnOff": {
+        "summary": "Command a particular streetlight to turn the lights on or off.",
+        "payload": {
+          "$ref": "#/components/schemas/turnOnOffPayload"
+        }
+      },
+      "dimLight": {
+        "summary": "Command a particular streetlight to dim the lights.",
+        "payload": {
+          "$ref": "#/components/schemas/dimLightPayload"
+        }
+      }
+    },
+    "schemas": {
+      "lightMeasuredPayload": {
+        "type": "object",
+        "properties": {
+          "lumens": {
+            "type": "integer",
+            "minimum": 0,
+            "description": "Light intensity measured in lumens."
+          },
+          "sentAt": {
+            "$ref": "#/components/schemas/sentAt"
+          }
+        }
+      },
+      "turnOnOffPayload": {
+        "type": "object",
+        "properties": {
+          "command": {
+            "type": "string",
+            "enum": [
+              "on",
+              "off"
+            ],
+            "description": "Whether to turn on or off the light."
+          },
+          "sentAt": {
+            "$ref": "#/components/schemas/sentAt"
+          }
+        }
+      },
+      "dimLightPayload": {
+        "type": "object",
+        "properties": {
+          "percentage": {
+            "type": "integer",
+            "description": "Percentage to which the light should be dimmed to.",
+            "minimum": 0,
+            "maximum": 100
+          },
+          "sentAt": {
+            "$ref": "#/components/schemas/sentAt"
+          }
+        }
+      },
+      "sentAt": {
+        "type": "string",
+        "format": "date-time",
+        "description": "Date and time when the message was sent."
+      }
+    },
+    "securitySchemes": {
+      "apiKey": {
+        "type": "apiKey",
+        "in": "user",
+        "description": "Provide your API key as the user and leave the password empty."
+      }
+    },
+    "parameters": {
+      "streetlightId": {
+        "name": "streetlightId",
+        "description": "The ID of the streetlight.",
+        "schema": {
+          "type": "string"
+        }
+      }
+    }
+  },
+  "channels": {
+    "smartylighting/streetlights/1/0/event/{streetlightId}/lighting/measured": {
+      "parameters": {
+        "streetlightId": {
+          "$ref": "#/components/parameters/streetlightId"
+        }
+      },
+      "publish": {
+        "message": {
+          "$ref": "#/components/messages/lightMeasured"
+        }
+      }
+    },
+    "smartylighting/streetlights/1/0/action/{streetlightId}/turn/on": {
+      "parameters": {
+        "streetlightId": {
+          "$ref": "#/components/parameters/streetlightId"
+        }
+      },
+      "subscribe": {
+        "message": {
+          "$ref": "#/components/messages/turnOnOff"
+        }
+      }
+    },
+    "smartylighting/streetlights/1/0/action/{streetlightId}/turn/off": {
+      "parameters": {
+        "streetlightId": {
+          "$ref": "#/components/parameters/streetlightId"
+        }
+      },
+      "subscribe": {
+        "message": {
+          "$ref": "#/components/messages/turnOnOff"
+        }
+      }
+    },
+    "smartylighting/streetlights/1/0/action/{streetlightId}/dim": {
+      "parameters": {
+        "streetlightId": {
+          "$ref": "#/components/parameters/streetlightId"
+        }
+      },
+      "subscribe": {
+        "message": {
+          "$ref": "#/components/messages/dimLight"
+        }
+      }
+    }
+  }
+}
\ No newline at end of file