diff --git a/adminer/include/bootstrap.inc.php b/adminer/include/bootstrap.inc.php
index 04fb5cdd..1a6f3c4d 100644
--- a/adminer/include/bootstrap.inc.php
+++ b/adminer/include/bootstrap.inc.php
@@ -1,5 +1,10 @@
 <?php
-error_reporting(6133); // errors
+function adminer_errors($errno, $errstr) {
+	return !!preg_match('~^(Trying to access array offset on value of type null|Undefined array key)~', $errstr);
+}
+
+error_reporting(6135); // errors and warnings
+set_error_handler('adminer_errors', 2); // 2 - E_WARNING
 
 include "../adminer/include/coverage.inc.php";
 
diff --git a/adminer/include/version.inc.php b/adminer/include/version.inc.php
index 8a0f069f..c2290e8a 100644
--- a/adminer/include/version.inc.php
+++ b/adminer/include/version.inc.php
@@ -1,2 +1,2 @@
 <?php
-$VERSION = "4.7.8";
+$VERSION = "4.7.9-dev";
diff --git a/changes.txt b/changes.txt
index 10eb654a..cb729dec 100644
--- a/changes.txt
+++ b/changes.txt
@@ -1,3 +1,6 @@
+Adminer 4.7.9-dev:
+Re-enable PHP warnings (regression from 4.7.8)
+
 Adminer 4.7.8 (released 2020-12-06):
 Support PHP 8
 Disallow connecting to privileged ports (bug #769)
diff --git a/compile.php b/compile.php
index 3bb1b6ac..574fe6ef 100755
--- a/compile.php
+++ b/compile.php
@@ -1,6 +1,11 @@
 #!/usr/bin/env php
 <?php
-error_reporting(6133); // errors
+function adminer_errors($errno, $errstr) {
+	return !!preg_match('~^(Trying to access array offset on value of type null|Undefined array key)~', $errstr);
+}
+
+error_reporting(6135); // errors and warnings
+set_error_handler('adminer_errors', 2); // 2 - E_WARNING
 include dirname(__FILE__) . "/adminer/include/version.inc.php";
 include dirname(__FILE__) . "/externals/JsShrink/jsShrink.php";
 
@@ -100,7 +105,7 @@ function lzw_compress($string) {
 	$word = "";
 	$codes = array();
 	for ($i=0; $i <= strlen($string); $i++) {
-		$x = $string[$i];
+		$x = @$string[$i];
 		if (strlen($x) && isset($dictionary[$word . $x])) {
 			$word .= $x;
 		} elseif ($i) {