diff --git a/javatests/com/google/re2j/ApiTestUtils.java b/javatests/com/google/re2j/ApiTestUtils.java
index b38b656d..a90e3c23 100644
--- a/javatests/com/google/re2j/ApiTestUtils.java
+++ b/javatests/com/google/re2j/ApiTestUtils.java
@@ -130,7 +130,7 @@ public static void testReplaceFirst(String orig, String regex, String repl, Stri
     Pattern p = Pattern.compile(regex);
     String replaced;
     for (MatcherInput input : Arrays.asList(MatcherInput.utf16(orig), MatcherInput.utf8(orig))) {
-      Matcher m = p.matcher(orig);
+      Matcher m = p.matcher(input);
       replaced = m.replaceFirst(repl);
       assertEquals(actual, replaced);
     }