diff --git a/closure/goog/testing/i18n/asserts.js b/closure/goog/testing/i18n/asserts.js
index a148eacfff..14dfe22380 100644
--- a/closure/goog/testing/i18n/asserts.js
+++ b/closure/goog/testing/i18n/asserts.js
@@ -121,6 +121,7 @@ goog.testing.i18n.asserts.assertI18nEquals = function(a, b, opt_c) {
 /**
  * Asserts that needle, or a string i18n-equivalent to needle, is a substring of
  * haystack. I18n-equivalent strings are set with addI18nMapping.
+ * Horizontal white space is removed before comparison.
  *
  * @param {string} needle The substring to search for.
  * @param {string} haystack The string to search within.
@@ -136,7 +137,11 @@ goog.testing.i18n.asserts.assertI18nContains = function(needle, haystack) {
     return;
   }
 
-  assertContains(needle, haystack);
+  const wsFixedNeedle = goog.testing.i18n.whitespace.removeWhitespace(needle);
+  const wsFixedHaystack =
+      goog.testing.i18n.whitespace.removeWhitespace(haystack);
+
+  assertContains(wsFixedNeedle, wsFixedHaystack);
 };
 
 
diff --git a/closure/goog/testing/i18n/asserts_test.js b/closure/goog/testing/i18n/asserts_test.js
index b9ee11bbe3..f79839b05e 100644
--- a/closure/goog/testing/i18n/asserts_test.js
+++ b/closure/goog/testing/i18n/asserts_test.js
@@ -89,6 +89,15 @@ testSuite({
     assertThrowsJsUnitException(() => {
       asserts.assertI18nEquals('mappedValue', '** dummy');
     });
+
+    // Check for containing with horizontal space matching
+
+    asserts.assertI18nContains('abc', ' abc\u1680');
+    asserts.assertI18nContains('abc', '\u202fabc \u3000');
+    asserts.assertI18nContains('abc', '\u202fabc \u3000');
+    asserts.assertI18nContains('a b c', '\u202fabc \u3000');
+    asserts.assertI18nContains('a\u202fb\t\xA0c', '\u202fabc \u3000');
+
   },
 
   testMappingWorks() {