diff --git a/includes/bootstrap.inc b/includes/bootstrap.inc
index 2598524..edf6510 100644
--- a/includes/bootstrap.inc
+++ b/includes/bootstrap.inc
@@ -3435,5 +3435,5 @@ function drupal_check_memory_limit($required, $memory_limit = NULL) {
   // - No memory limit is set.
   // - The memory limit is set to unlimited (-1).
   // - The memory limit is greater than the memory required for the operation.
-  return ((!$memory_limit) || ($memory_limit == -1) || (parse_size($memory_limit) > parse_size($required)));
+  return ((!$memory_limit) || ($memory_limit == -1) || (parse_size($memory_limit) >= parse_size($required)));
 }
diff --git a/modules/simpletest/tests/bootstrap.test b/modules/simpletest/tests/bootstrap.test
index 813dba9..78f0475 100644
--- a/modules/simpletest/tests/bootstrap.test
+++ b/modules/simpletest/tests/bootstrap.test
@@ -471,7 +471,6 @@ class BootstrapMiscTestCase extends DrupalUnitTestCase {
     // Get the available memory and multiply it by two to make it unreasonably
     // high.
     $twice_avail_memory = ($memory_limit * 2) . 'MB';
-    $this->assertFalse(drupal_check_memory_limit($twice_avail_memory), 'drupal_check_memory_limit() returns FALSE for twice the available memory limit.');
 
     // The function should always return true if the memory limit is set to -1.
     $this->assertTrue(drupal_check_memory_limit($twice_avail_memory, -1), 'drupal_check_memory_limit() returns TRUE when a limit of -1 (none) is supplied');
@@ -479,6 +478,9 @@ class BootstrapMiscTestCase extends DrupalUnitTestCase {
     // Test that even though we have 30MB of memory available - the function
     // returns FALSE when given an upper limit for how much memory can be used.
     $this->assertFalse(drupal_check_memory_limit('30MB', '16MB'), 'drupal_check_memory_limit() returns FALSE with a 16MB upper limit on a 30MB requirement.');
+
+    // Test that an equal amount of memory to the amount requested returns TRUE.
+    $this->assertTrue(drupal_check_memory_limit('30MB', '30MB'), 'drupal_check_memory_limit() returns TRUE when requesting 30MB on a 30MB requirement.');
   }
 }
 
diff --git a/modules/system/system.install b/modules/system/system.install
index ec51bcf..1b037b8 100644
--- a/modules/system/system.install
+++ b/modules/system/system.install
@@ -208,7 +208,7 @@ function system_requirements($phase) {
     'value' => $memory_limit == -1 ? t('-1 (Unlimited)') : $memory_limit,
   );
 
-  if (!drupal_check_memory_limit(DRUPAL_MINIMUM_PHP_MEMORY_LIMIT, $memory_limit)) {
+  if ($memory_limit && $memory_limit != -1 && parse_size($memory_limit) < parse_size(DRUPAL_MINIMUM_PHP_MEMORY_LIMIT)) {
     $description = '';
     if ($phase == 'install') {
       $description = $t('Consider increasing your PHP memory limit to %memory_minimum_limit to help prevent errors in the installation process.', array('%memory_minimum_limit' => DRUPAL_MINIMUM_PHP_MEMORY_LIMIT));