diff --git a/src/Symfony/Component/Console/Terminal.php b/src/Symfony/Component/Console/Terminal.php
index 24cef534052f1..04653d3bd2bbc 100644
--- a/src/Symfony/Component/Console/Terminal.php
+++ b/src/Symfony/Component/Console/Terminal.php
@@ -77,7 +77,8 @@ public static function hasSttyAvailable(): bool
     private static function initDimensions()
     {
         if ('\\' === \DIRECTORY_SEPARATOR) {
-            if (preg_match('/^(\d+)x(\d+)(?: \((\d+)x(\d+)\))?$/', trim(getenv('ANSICON')), $matches)) {
+            $ansicon = getenv('ANSICON');
+            if (false !== $ansicon && preg_match('/^(\d+)x(\d+)(?: \((\d+)x(\d+)\))?$/', trim($ansicon), $matches)) {
                 // extract [w, H] from "wxh (WxH)"
                 // or [w, h] from "wxh"
                 self::$width = (int) $matches[1];