diff --git a/src/rules/extensions.js b/src/rules/extensions.js
index fef898b5a..4c45ada57 100644
--- a/src/rules/extensions.js
+++ b/src/rules/extensions.js
@@ -96,7 +96,7 @@ module.exports = {
   create: function (context) {
 
     const props = buildProperties(context)
-    
+
     function getModifier(extension) {
       return props.pattern[extension] || props.defaultConfig
     }
@@ -131,11 +131,10 @@ module.exports = {
       const extension = path.extname(resolvedPath || importPath).substring(1)
 
       // determine if this is a module
-      const isPackageMain = 
-        isExternalModuleMain(importPath, context.settings) || 
-        isScopedMain(importPath)
+      const isPackageMain = isExternalModuleMain(importPath, context.settings)
+        || isScopedMain(importPath)
 
-      if (!extension || !importPath.endsWith(extension)) {
+      if (!extension || !importPath.endsWith(`.${extension}`)) {
         const extensionRequired = isUseOfExtensionRequired(extension, isPackageMain)
         const extensionForbidden = isUseOfExtensionForbidden(extension)
         if (extensionRequired && !extensionForbidden) {
diff --git a/tests/files/internal-modules/package.json b/tests/files/internal-modules/package.json
new file mode 100644
index 000000000..e69de29bb
diff --git a/tests/files/node_modules/exceljs/excel.js b/tests/files/node_modules/exceljs/excel.js
new file mode 100644
index 000000000..e69de29bb
diff --git a/tests/files/node_modules/exceljs/package.json b/tests/files/node_modules/exceljs/package.json
new file mode 100644
index 000000000..70d59eaaa
--- /dev/null
+++ b/tests/files/node_modules/exceljs/package.json
@@ -0,0 +1,3 @@
+{
+  "main": "./excel.js"
+}
diff --git a/tests/src/rules/extensions.js b/tests/src/rules/extensions.js
index 1b47066f7..d34f7e1b5 100644
--- a/tests/src/rules/extensions.js
+++ b/tests/src/rules/extensions.js
@@ -1,6 +1,6 @@
 import { RuleTester } from 'eslint'
 import rule from 'rules/extensions'
-import { test } from '../utils'
+import { test, testFilePath } from '../utils'
 
 const ruleTester = new RuleTester()
 
@@ -59,7 +59,6 @@ ruleTester.run('extensions', rule, {
     test({ code: 'import thing from "./fake-file.js"', options: [ 'always' ] }),
     test({ code: 'import thing from "non-package"', options: [ 'never' ] }),
 
-
     test({
       code: `
         import foo from './foo.js'
@@ -90,6 +89,17 @@ ruleTester.run('extensions', rule, {
       options: [ 'never', {ignorePackages: true} ],
     }),
 
+    test({
+      code: 'import exceljs from "exceljs"',
+      options: [ 'always', { js: 'never', jsx: 'never' } ],
+      filename: testFilePath('./internal-modules/plugins/plugin.js'),
+      settings: {
+        'import/resolver': {
+          'node': { 'extensions': [ '.js', '.jsx', '.json' ] },
+          'webpack': { 'config': 'webpack.empty.config.js' },
+        },
+      },
+    }),
   ],
 
   invalid: [