diff --git a/core/util.inc.php b/core/util.inc.php
index fdf97a31..a01c52b2 100644
--- a/core/util.inc.php
+++ b/core/util.inc.php
@@ -1276,7 +1276,7 @@ function _end_coverage() {
 		$n = 0;
 		$t = time();
 		while(file_exists("$absolute_path/$t.$n.log")) $n++;
-		file_put_contents("$absolute_path/$t.$n.log", serialize(xdebug_get_code_coverage()));
+		file_put_contents("$absolute_path/$t.$n.log", gzdeflate(serialize(xdebug_get_code_coverage())));
 	}
 }
 ?>