diff --git a/tests/i18n/i18nTextCollectorTest.php b/tests/i18n/i18nTextCollectorTest.php
index 46ccfa9e6..f7c98374d 100644
--- a/tests/i18n/i18nTextCollectorTest.php
+++ b/tests/i18n/i18nTextCollectorTest.php
@@ -407,6 +407,11 @@ PHP;
 	}
 	
 	function testCollectFromFilesystemAndWriteMasterTables() {
+		$defaultlocal = i18n::default_locale();
+		$local = i18n::get_locale();
+		i18n::set_locale('en_US');  //set the locale to the US locale expected in the asserts
+		i18n::set_default_locale('en_US');
+
 		$c = new i18nTextCollector();
 		$c->basePath = $this->alternateBasePath;
 		$c->baseSavePath = $this->alternateBaseSavePath;
@@ -466,6 +471,9 @@ PHP;
 			"\$lang['en_US']['i18nOtherModule']['MAINTEMPLATE'] = 'Main Template Other Module';",
 			$otherModuleLangFileContent
 		);
+
+		i18n::set_locale($local);  //set the locale to the US locale expected in the asserts
++		i18n::set_default_locale($defaultlocal);
 	}
 	
 	function testCollectFromEntityProvidersInCustomObject() {
diff --git a/tests/model/MoneyTest.php b/tests/model/MoneyTest.php
index 4018503a5..55fa413a3 100644
--- a/tests/model/MoneyTest.php
+++ b/tests/model/MoneyTest.php
@@ -74,6 +74,9 @@ class MoneyTest extends SapphireTest {
      * is re-read properly.
      */
     function testGettingWrittenDataObject() {
+	    $local = i18n::get_locale();
+		i18n::set_locale('en_US');  //make sure that the $ amount is not prefixed by US$, as it would be in non-US locale
+
 		$obj = new MoneyTest_DataObject();
 		
 		$m = new Money();
@@ -93,6 +96,8 @@ class MoneyTest extends SapphireTest {
 		$this->assertEquals("$987.65", $moneyTest->MyMoney->Nice(),
 			"Money field not added to data object properly when read."
 		);
+
+	    i18n::set_locale($local);
     }
 	
 	public function testToCurrency() {
diff --git a/tests/security/MemberTest.php b/tests/security/MemberTest.php
index a8f921cdf..1456c5f04 100644
--- a/tests/security/MemberTest.php
+++ b/tests/security/MemberTest.php
@@ -7,7 +7,22 @@ class MemberTest extends FunctionalTest {
 	static $fixture_file = 'sapphire/tests/security/MemberTest.yml';
 	
 	protected $orig = array();
-	
+	protected $local = null; 
+
+	function __construct() {
+		parent::__construct();
+
+		//Setting the locale has to happen in the constructor (using the setUp and tearDown methods doesn't work)
+		//This is because the test relies on the yaml file being interpreted according to a particular date format
+		//and this setup occurs before the setUp method is run 
+		$this->local = i18n::default_locale();
+		i18n::set_default_locale('en_US');
+	}
+
+	function __destruct() {
+        i18n::set_default_locale($this->local);
+    }
+
 	function setUp() {
 		parent::setUp();
 		
@@ -18,7 +33,7 @@ class MemberTest extends FunctionalTest {
 	
 	function tearDown() {
 		Member::set_unique_identifier_field($this->orig['Member_unique_identifier_field']);
-		
+
 		parent::tearDown();
 	}
 
diff --git a/tests/security/SecurityTest.php b/tests/security/SecurityTest.php
index e3b5c84dd..6e1b058ea 100644
--- a/tests/security/SecurityTest.php
+++ b/tests/security/SecurityTest.php
@@ -183,6 +183,9 @@ class SecurityTest extends FunctionalTest {
 	}
 		
 	function testRepeatedLoginAttemptsLockingPeopleOut() {
+		$local = i18n::get_locale();
+		i18n::set_locale('en_US');
+
 		Member::lock_out_after_incorrect_logins(5);
 		
 		/* LOG IN WITH A BAD PASSWORD 7 TIMES */
@@ -239,6 +242,8 @@ class SecurityTest extends FunctionalTest {
 		
 		$this->doTestLoginForm('sam@silverstripe.com' , '1nitialPassword');
 		$this->assertEquals($this->session()->inst_get('loggedInAs'), $member->ID);
+
+		i18n::set_locale($local);
 	}
 	
 	function testAlternatingRepeatedLoginAttempts() {