diff --git a/core/startup/ErrorControlChain.php b/core/startup/ErrorControlChain.php
index 86a149e45..8925c3239 100644
--- a/core/startup/ErrorControlChain.php
+++ b/core/startup/ErrorControlChain.php
@@ -77,13 +77,35 @@ class ErrorControlChain {
 	 */
 	public function setSuppression($suppression) {
 		$this->suppression = (bool)$suppression;
-		// Don't modify errors unless handling fatal errors, and if errors were
-		// originally allowed to be displayed.
-		if ($this->handleFatalErrors && $this->originalDisplayErrors) {
-			ini_set('display_errors', !$suppression);
+		// If handling fatal errors, conditionally disable, or restore error display
+		// Note: original value of display_errors could also evaluate to "off"
+		if ($this->handleFatalErrors) {
+			if($suppression) {
+				$this->setDisplayErrors(0);
+			} else {
+				$this->setDisplayErrors($this->originalDisplayErrors);
+			}
 		}
 	}
 
+	/**
+	 * Set display_errors
+	 *
+	 * @param mixed $errors
+	 */
+	protected function setDisplayErrors($errors) {
+		ini_set('display_errors', $errors);
+	}
+
+	/**
+	 * Get value of display_errors ini value
+	 *
+	 * @return mixed
+	 */
+	protected function getDisplayErrors() {
+		return ini_get('display_errors');
+	}
+
 	/**
 	 * Add this callback to the chain of callbacks to call along with the state
 	 * that $error must be in this point in the chain for the callback to be called
@@ -178,7 +200,7 @@ class ErrorControlChain {
 		register_shutdown_function(array($this, 'handleFatalError'));
 		$this->handleFatalErrors = true;
 
-		$this->originalDisplayErrors = ini_get('display_errors');
+		$this->originalDisplayErrors = $this->getDisplayErrors();
 		$this->setSuppression($this->suppression);
 
 		$this->step();
@@ -202,7 +224,7 @@ class ErrorControlChain {
 		else {
 			// Now clean up
 			$this->handleFatalErrors = false;
-			ini_set('display_errors', $this->originalDisplayErrors);
+			$this->setDisplayErrors($this->originalDisplayErrors);
 		}
 	}
 }
diff --git a/tests/core/startup/ErrorControlChainTest.php b/tests/core/startup/ErrorControlChainTest.php
index a6c2c2496..4f550c548 100644
--- a/tests/core/startup/ErrorControlChainTest.php
+++ b/tests/core/startup/ErrorControlChainTest.php
@@ -8,6 +8,30 @@
  */
 class ErrorControlChainTest_Chain extends ErrorControlChain {
 
+	protected $displayErrors = 'STDERR';
+
+	/**
+	 * Modify method visibility to public for testing
+	 *
+	 * @return string
+	 */
+	public function getDisplayErrors()
+	{
+		// Protect manipulation of underlying php_ini values
+		return $this->displayErrors;
+	}
+
+	/**
+	 * Modify method visibility to public for testing
+	 *
+	 * @param mixed $errors
+	 */
+	public function setDisplayErrors($errors)
+	{
+		// Protect manipulation of underlying php_ini values
+		$this->displayErrors = $errors;
+	}
+
 	// Change function visibility to be testable directly
 	public function translateMemstring($memstring) {
 		return parent::translateMemstring($memstring);
@@ -63,10 +87,7 @@ require_once '$classpath';
 
 class ErrorControlChainTest extends SapphireTest {
 
-	protected $displayErrors = null;
-
 	function setUp() {
-		$this->displayErrors = (bool)ini_get('display_errors');
 
 		// Check we can run PHP at all
 		$null = is_writeable('/dev/null') ? '/dev/null' : 'NUL';
@@ -80,50 +101,55 @@ class ErrorControlChainTest extends SapphireTest {
 		parent::setUp();
 	}
 
-	public function tearDown() {
-		if($this->displayErrors !== null) {
-			ini_set('display_errors', $this->displayErrors);
-			$this->displayErrors = null;
-		}
-		parent::tearDown(); // TODO: Change the autogenerated stub
-	}
-
 	function testErrorSuppression() {
 
 		// Errors disabled by default
-		ini_set('display_errors', false);
-		$chain = new ErrorControlChain();
+		$chain = new ErrorControlChainTest_Chain();
+		$chain->setDisplayErrors('Off'); // mocks display_errors: Off
+		$initialValue = null;
 		$whenNotSuppressed = null;
 		$whenSuppressed = null;
-		$chain->then(function($chain) use(&$whenNotSuppressed, &$whenSuppressed) {
-			$chain->setSuppression(true);
-			$whenSuppressed = ini_get('display_errors');
-			$chain->setSuppression(false);
-			$whenNotSuppressed = ini_get('display_errors');
-		})->execute();
+		$chain->then(
+			function(ErrorControlChainTest_Chain $chain)
+				use(&$initialValue, &$whenNotSuppressed, &$whenSuppressed) {
+					$initialValue = $chain->getDisplayErrors();
+					$chain->setSuppression(false);
+					$whenNotSuppressed = $chain->getDisplayErrors();
+					$chain->setSuppression(true);
+					$whenSuppressed = $chain->getDisplayErrors();
+				}
+		)->execute();
 
 		// Disabled errors never un-disable
-		$this->assertFalse((bool)$whenNotSuppressed);
-		$this->assertFalse((bool)$whenSuppressed);
+		$this->assertEquals(0, $initialValue); // Chain starts suppressed
+		$this->assertEquals(0, $whenSuppressed); // false value used internally when suppressed
+		$this->assertEquals('Off', $whenNotSuppressed); // false value set by php ini when suppression lifted
+		$this->assertEquals('Off', $chain->getDisplayErrors()); // Correctly restored after run
 
 		// Errors enabled by default
-		ini_set('display_errors', true);
-		$chain = new ErrorControlChain();
+		$chain = new ErrorControlChainTest_Chain();
+		$chain->setDisplayErrors('Yes'); // non-falsey ini value
+		$initialValue = null;
 		$whenNotSuppressed = null;
 		$whenSuppressed = null;
-		$chain->then(function($chain) use(&$whenNotSuppressed, &$whenSuppressed) {
-			$chain->setSuppression(true);
-			$whenSuppressed = ini_get('display_errors');
-			$chain->setSuppression(false);
-			$whenNotSuppressed = ini_get('display_errors');
-		})->execute();
+		$chain->then(
+			function(ErrorControlChainTest_Chain $chain)
+				use(&$initialValue, &$whenNotSuppressed, &$whenSuppressed) {
+					$initialValue = $chain->getDisplayErrors();
+					$chain->setSuppression(true);
+					$whenSuppressed = $chain->getDisplayErrors();
+					$chain->setSuppression(false);
+					$whenNotSuppressed = $chain->getDisplayErrors();
+				}
+		)->execute();
 
 		// Errors can be suppressed an un-suppressed when initially enabled
-		$this->assertTrue((bool)$whenNotSuppressed);
-		$this->assertFalse((bool)$whenSuppressed);
+		$this->assertEquals(0, $initialValue); // Chain starts suppressed
+		$this->assertEquals(0, $whenSuppressed); // false value used internally when suppressed
+		$this->assertEquals('Yes', $whenNotSuppressed); // false value set by php ini when suppression lifted
+		$this->assertEquals('Yes', $chain->getDisplayErrors()); // Correctly restored after run
 
 		// Fatal error
-
 		$chain = new ErrorControlChainTest_Chain();
 
 		list($out, $code) = $chain