diff --git a/lib/moodlelib.php b/lib/moodlelib.php
index fa8101229d8..3abb77d2621 100644
--- a/lib/moodlelib.php
+++ b/lib/moodlelib.php
@@ -8197,18 +8197,45 @@ function check_php_version($version='5.2.4') {
 
 
       case 'Gecko':   /// Gecko based browsers
-          if (empty($version) and substr_count($agent, 'Camino')) {
-              // MacOS X Camino support
-              $version = 20041110;
+          // Do not look for dates any more, we expect real Firefox version here.
+          if (empty($version)) {
+              $version = 1;
+          } else if ($version > 20000000) {
+              // This is just a guess, it is not supposed to be 100% accurate!
+              if (preg_match('/^201/', $version)) {
+                  $version = 3.6;
+              } else if (preg_match('/^200[7-9]/', $version)) {
+                  $version = 3;
+              } else if (preg_match('/^2006/', $version)) {
+                  $version = 2;
+              } else {
+                  $version = 1.5;
+              }
           }
-
-          // the proper string - Gecko/CCYYMMDD Vendor/Version
-          // Faster version and work-a-round No IDN problem.
-          if (preg_match("/Gecko\/([0-9]+)/i", $agent, $match)) {
-              if ($match[1] > $version) {
-                      return true;
+          if (preg_match("/(Iceweasel|Firefox)\/([0-9\.]+)/i", $agent, $match)) {
+              // Use real Firefox version if specified in user agent string.
+              if (version_compare($match[2], $version) >= 0) {
+                  return true;
+              }
+          } else if (preg_match("/Gecko\/([0-9\.]+)/i", $agent, $match)) {
+              // Gecko might contain date or Firefox revision, let's just guess the Firefox version from the date.
+              $browserver = $match[1];
+              if ($browserver > 20000000) {
+                  // This is just a guess, it is not supposed to be 100% accurate!
+                  if (preg_match('/^201/', $browserver)) {
+                      $browserver = 3.6;
+                  } else if (preg_match('/^200[7-9]/', $browserver)) {
+                      $browserver = 3;
+                  } else if (preg_match('/^2006/', $version)) {
+                      $browserver = 2;
+                  } else {
+                      $browserver = 1.5;
                   }
               }
+              if (version_compare($browserver, $version) >= 0) {
+                  return true;
+              }
+          }
           break;