diff --git a/lib/classes/date.php b/lib/classes/date.php
index 6026bb91e72..3685809eb4f 100644
--- a/lib/classes/date.php
+++ b/lib/classes/date.php
@@ -134,7 +134,7 @@ class core_date {
             // Convert to known zone.
             $tz = self::$badzones[$tz];
             $fixed = true;
-        } else if (is_number($tz)) {
+        } else if (is_numeric($tz)) {
             // Half hour numeric offsets were already tested, try rounding to integers here.
             $roundedtz = (string)(int)$tz;
             if (isset(self::$badzones[$roundedtz])) {
diff --git a/lib/tests/date_legacy_test.php b/lib/tests/date_legacy_test.php
index 09ddf026a84..758416373a9 100644
--- a/lib/tests/date_legacy_test.php
+++ b/lib/tests/date_legacy_test.php
@@ -339,5 +339,9 @@ class core_date_legacy_testcase extends advanced_testcase {
 
         $USER->timezone = 'Europe/Prague';
         $this->assertSame('Europe/Prague', usertimezone('99'));
+
+        // Checking fallback with an unexisting timezone.
+        $USER->timezone = '-9.23';
+        $this->assertSame('UTC-9', usertimezone('99'));
     }
 }