diff --git a/docs/deprecations.md b/docs/deprecations.md
index 4bdfc1b19..feebfd3f4 100644
--- a/docs/deprecations.md
+++ b/docs/deprecations.md
@@ -36,6 +36,14 @@ Note:
 - In service configuration setting is ineffective for deprecations reported before service configuration is read.
 - `SLS_DEPRECATION_DISABLE` env var and `disabledDeprecations` configuration setting remain respected, and no errors will be thrown for mentioned deprecation coodes.
 
+<a name="DUPLICATE_PLUGIN_DEFINITION"><div>&nbsp;</div></a>
+
+## Duplicate plugin definition in configuration
+
+Deprecation code: `DUPLICATE_PLUGIN_DEFINITION`
+
+Starting with "v3.0.0", duplicate plugin definition will result in an error instead of a warning. To ensure seamless upgrade, please remove duplicate plugins from your configuration.
+
 <a name="CLI_VERBOSE_OPTION_ALIAS"><div>&nbsp;</div></a>
 
 ## CLI `-v` alias for `--verbose` option
diff --git a/lib/classes/PluginManager.js b/lib/classes/PluginManager.js
index 02588a5cb..38992dcd7 100644
--- a/lib/classes/PluginManager.js
+++ b/lib/classes/PluginManager.js
@@ -133,9 +133,9 @@ class PluginManager {
 
     // don't load plugins twice
     if (this.plugins.some((plugin) => plugin instanceof Plugin)) {
-      legacy.log(`WARNING: duplicate plugin ${Plugin.name} was not loaded\n`);
-      log.warning(
-        `Duplicate plugin definition found in your configuration. Plugin "${Plugin.name}" will not be loaded more than once.`
+      this.serverless._logDeprecation(
+        'DUPLICATE_PLUGIN_DEFINITION',
+        'Starting with "v3.0.0", duplicate plugin definition will result in an error instead of a warning. To ensure seamless upgrade, please remove duplicate plugins from your configuration.'
       );
       return null;
     }
diff --git a/test/unit/lib/classes/PluginManager.test.js b/test/unit/lib/classes/PluginManager.test.js
index cc89f44ee..a1c4b4d72 100644
--- a/test/unit/lib/classes/PluginManager.test.js
+++ b/test/unit/lib/classes/PluginManager.test.js
@@ -568,14 +568,6 @@ describe('PluginManager', () => {
       expect(pluginManager.plugins[0]).to.be.instanceof(SynchronousPluginMock);
     });
 
-    it('should not load plugins twice', () => {
-      pluginManager.addPlugin(SynchronousPluginMock);
-      pluginManager.addPlugin(SynchronousPluginMock);
-
-      expect(pluginManager.plugins[0]).to.be.instanceof(SynchronousPluginMock);
-      expect(pluginManager.plugins.length).to.equal(1);
-    });
-
     it('should load two plugins that happen to have the same class name', () => {
       function getFirst() {
         return class PluginMock {};