diff --git a/src/ProcessManager/ChromeManager.php b/src/ProcessManager/ChromeManager.php
index 0c1b1772..df4a9787 100644
--- a/src/ProcessManager/ChromeManager.php
+++ b/src/ProcessManager/ChromeManager.php
@@ -97,7 +97,7 @@ private function getDefaultArguments(): array
         $args = [];
 
         // Enable the headless mode unless PANTHER_NO_HEADLESS is defined
-        if ($_SERVER['PANTHER_NO_HEADLESS'] ?? true) {
+        if (!($_SERVER['PANTHER_NO_HEADLESS'] ?? false)) {
             $args[] = '--headless';
             $args[] = '--window-size=1200,1100';
             $args[] = '--disable-gpu';
diff --git a/src/ProcessManager/FirefoxManager.php b/src/ProcessManager/FirefoxManager.php
index 9821154f..9a15477d 100644
--- a/src/ProcessManager/FirefoxManager.php
+++ b/src/ProcessManager/FirefoxManager.php
@@ -92,7 +92,7 @@ private function getDefaultArguments(): array
         $args = [];
 
         // Enable the headless mode unless PANTHER_NO_HEADLESS is defined
-        if ($_SERVER['PANTHER_NO_HEADLESS'] ?? true) {
+        if (!($_SERVER['PANTHER_NO_HEADLESS'] ?? false)) {
             $args[] = '--headless';
             $args[] = '--window-size=1200,1100';
         }