diff --git a/requirement-checker/src/Terminal.php b/requirement-checker/src/Terminal.php
index 2cf1690ee..863d06a1f 100644
--- a/requirement-checker/src/Terminal.php
+++ b/requirement-checker/src/Terminal.php
@@ -96,7 +96,7 @@ public static function hasSttyAvailable(): bool
     private static function initDimensions(): void
     {
         if ('\\' === DIRECTORY_SEPARATOR) {
-            if (preg_match('/^(\d+)x(\d+)(?: \((\d+)x(\d+)\))?$/', trim(getenv('ANSICON')), $matches)) {
+            if (preg_match('/^(\d+)x(\d+)(?: \((\d+)x(\d+)\))?$/', trim(getenv('ANSICON') ?: ''), $matches)) {
                 // extract [w, H] from "wxh (WxH)"
                 // or [w, h] from "wxh"
                 self::$width = (int) $matches[1];