diff --git a/src/EnvironmentSetCommand.php b/src/EnvironmentSetCommand.php
index ab89487..72b96af 100644
--- a/src/EnvironmentSetCommand.php
+++ b/src/EnvironmentSetCommand.php
@@ -80,8 +80,9 @@ public function setEnvVariable(string $envFileContent, string $key, string $valu
         $oldPair = $this->readKeyValuePair($envFileContent, $key);
 
         // Wrap values that have a space or equals in quotes to escape them
-        if (preg_match('/\s/',$value) || strpos($value, '=') !== false) {
-            $value = '"' . $value . '"';
+        $trimmedValue = trim($value);
+        if (!str_starts_with($trimmedValue, '"') && !str_ends_with($trimmedValue, '"') && preg_match('/\s/',$value) || strpos($value, '=') !== false) {
+            $value = '"' . str_replace('"', '\"', $value) . '"';
         }
 
         $newPair = $key . '=' . $value;
diff --git a/tests/Unit/EnvironmentSetCommandTest.php b/tests/Unit/EnvironmentSetCommandTest.php
index d0d3c28..ae95a36 100644
--- a/tests/Unit/EnvironmentSetCommandTest.php
+++ b/tests/Unit/EnvironmentSetCommandTest.php
@@ -70,6 +70,19 @@ public function testWhitespaceAsValueDoesntCreateNewEntry(): void
         $this->assertEquals($expectedEnv, $newEnv);
     }
 
+    /**
+     * @covers EnvironmentSetCommand::setEnvVariable
+     */
+    public function testQuotedCharactersArePreserved(): void
+    {
+        $env = 'APP_NAME=' . "\n";
+
+        $expectedEnv = 'APP_NAME="MY.NAME & C."' . "\n";
+
+        [$newEnv, $_] = $this->command->setEnvVariable($env, 'APP_NAME', 'MY.NAME & C.');
+        $this->assertEquals($expectedEnv, $newEnv);
+    }
+
     /**
      * @covers       EnvironmentSetCommand::readKeyValuePair
      * @dataProvider readKeyValuePairDataProvider