diff --git a/Dotenv.php b/Dotenv.php
index f249ca8..2c76d52 100644
--- a/Dotenv.php
+++ b/Dotenv.php
@@ -151,7 +151,7 @@ public function bootEnv(string $path, string $defaultEnv = 'dev', array $testEnv
         $env = is_file($p) ? include $p : null;
         $k = $this->envKey;
 
-        if (\is_array($env) && (!isset($env[$k]) || ($_SERVER[$k] ?? $_ENV[$k] ?? $env[$k]) === $env[$k])) {
+        if (\is_array($env) && ($overrideExistingVars || !isset($env[$k]) || ($_SERVER[$k] ?? $_ENV[$k] ?? $env[$k]) === $env[$k])) {
             $this->populate($env, $overrideExistingVars);
         } else {
             $this->loadEnv($path, $k, $defaultEnv, $testEnvs, $overrideExistingVars);
diff --git a/Tests/DotenvTest.php b/Tests/DotenvTest.php
index 4345792..47c9bfb 100644
--- a/Tests/DotenvTest.php
+++ b/Tests/DotenvTest.php
@@ -587,6 +587,13 @@ public function testBootEnv()
         $this->assertSame('BAR', $_SERVER['FOO']);
         $this->assertSame('1', $_SERVER['TEST_APP_DEBUG']);
         $this->assertSame('localphpNEW_VALUE', $_SERVER['EXISTING_KEY']);
+
+        $resetContext();
+        $_SERVER['TEST_APP_ENV'] = 'ccc';
+        (new Dotenv('TEST_APP_ENV', 'TEST_APP_DEBUG'))->bootEnv($path, 'dev', ['test'], true);
+        $this->assertSame('BAR', $_SERVER['FOO']);
+        $this->assertSame('1', $_SERVER['TEST_APP_DEBUG']);
+        $this->assertSame('localphpNEW_VALUE', $_SERVER['EXISTING_KEY']);
         unlink($path.'.local.php');
 
         $resetContext();