diff --git a/core/modules/color/color.module b/core/modules/color/color.module
index defff00..b2b67a7 100644
--- a/core/modules/color/color.module
+++ b/core/modules/color/color.module
@@ -324,9 +324,10 @@ function color_scheme_form_submit($form, &$form_state) {
     // memory_get_usage(), therefore we won't inadvertently reject a color
     // scheme change based on a faulty memory calculation.
     $usage = memory_get_usage(TRUE);
-    $memory_limit = parse_size(ini_get('memory_limit'));
-    if (!drupal_check_memory_limit($usage + $required)) {
-      drupal_set_message(t('There is not enough memory available to PHP to change this theme\'s color scheme. You need at least %size more. Check the <a href="@url">PHP documentation</a> for more information.', array('%size' => format_size($usage + $required - $memory_limit), '@url' => 'http://www.php.net/manual/ini.core.php#ini.sect.resource-limits')), 'error');
+    $memory_limit = ini_get('memory_limit');
+    $size = parse_size($memory_limit);
+    if (!drupal_check_memory_limit($usage + $required, $memory_limit)) {
+      drupal_set_message(t('There is not enough memory available to PHP to change this theme\'s color scheme. You need at least %size more. Check the <a href="@url">PHP documentation</a> for more information.', array('%size' => format_size($usage + $required - $size), '@url' => 'http://www.php.net/manual/ini.core.php#ini.sect.resource-limits')), 'error');
       return;
     }
   }
diff --git a/core/modules/simpletest/simpletest.install b/core/modules/simpletest/simpletest.install
index 60f54d4..23db4dc 100644
--- a/core/modules/simpletest/simpletest.install
+++ b/core/modules/simpletest/simpletest.install
@@ -63,7 +63,7 @@ function simpletest_requirements($phase) {
   // Check the current memory limit. If it is set too low, SimpleTest will fail
   // to load all tests and throw a fatal error.
   $memory_limit = ini_get('memory_limit');
-  if (!drupal_check_memory_limit(SIMPLETEST_MINIMUM_PHP_MEMORY_LIMIT)) {
+  if (!drupal_check_memory_limit(SIMPLETEST_MINIMUM_PHP_MEMORY_LIMIT, $memory_limit)) {
     $requirements['php_memory_limit']['severity'] = REQUIREMENT_ERROR;
     $requirements['php_memory_limit']['description'] = $t('The testing framework requires the PHP memory limit to be at least %memory_minimum_limit. The current value is %memory_limit. <a href="@url">Follow these steps to continue</a>.', array('%memory_limit' => $memory_limit, '%memory_minimum_limit' => SIMPLETEST_MINIMUM_PHP_MEMORY_LIMIT, '@url' => 'http://drupal.org/node/207036'));
   }
diff --git a/core/modules/system/system.install b/core/modules/system/system.install
index 9dd842c..1dde47f 100644
--- a/core/modules/system/system.install
+++ b/core/modules/system/system.install
@@ -201,7 +201,7 @@ function system_requirements($phase) {
     'value' => $memory_limit == -1 ? t('-1 (Unlimited)') : $memory_limit,
   );
 
-  if (!drupal_check_memory_limit(DRUPAL_MINIMUM_PHP_MEMORY_LIMIT)) {
+  if (!drupal_check_memory_limit(DRUPAL_MINIMUM_PHP_MEMORY_LIMIT, $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));
diff --git a/core/modules/system/tests/bootstrap.test b/core/modules/system/tests/bootstrap.test
index 65c8ad2..c305a06 100644
--- a/core/modules/system/tests/bootstrap.test
+++ b/core/modules/system/tests/bootstrap.test
@@ -477,12 +477,13 @@ class BootstrapMiscTestCase extends DrupalUnitTestCase {
    * Tests that the drupal_check_memory_limit() function works as expected.
    */
   function testCheckMemoryLimit() {
+    $memory_limit = ini_get('memory_limit');
     // Test that a very reasonable amount of memory is available.
     $this->assertTrue(drupal_check_memory_limit('30MB'), '30MB of memory tested available.');
 
     // Get the available memory and multiply it by two to make it unreasonably
     // high.
-    $twice_avail_memory = (ini_get('memory_limit') * 2) . 'MB';
+    $twice_avail_memory = ($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.