diff --git a/okhttp-tests/src/test/java/okhttp3/HeadersTest.java b/okhttp-tests/src/test/java/okhttp3/HeadersTest.java
index fc134f49e..494ac90b8 100644
--- a/okhttp-tests/src/test/java/okhttp3/HeadersTest.java
+++ b/okhttp-tests/src/test/java/okhttp3/HeadersTest.java
@@ -430,7 +430,7 @@ public final class HeadersTest {
         .build();
     List<Challenge> challenges = HttpHeaders.parseChallenges(headers, "WWW-Authenticate");
     assertEquals(1, challenges.size());
-    assertEquals("digest", challenges.get(0).scheme());
+    assertEquals("Digest", challenges.get(0).scheme());
     assertEquals("myrealm", challenges.get(0).realm());
     Map<String, String> expectedAuthParams = new LinkedHashMap<>();
     expectedAuthParams.put("realm", "myrealm");
@@ -447,7 +447,7 @@ public final class HeadersTest {
         .build();
     List<Challenge> challenges = HttpHeaders.parseChallenges(headers, "WWW-Authenticate");
     assertEquals(1, challenges.size());
-    assertEquals("digest", challenges.get(0).scheme());
+    assertEquals("Digest", challenges.get(0).scheme());
     assertEquals("myrealm", challenges.get(0).realm());
     Map<String, String> expectedAuthParams = new LinkedHashMap<>();
     expectedAuthParams.put("realm", "myrealm");
@@ -464,7 +464,7 @@ public final class HeadersTest {
         .build();
     List<Challenge> challenges = HttpHeaders.parseChallenges(headers, "WWW-Authenticate");
     assertEquals(1, challenges.size());
-    assertEquals("digest", challenges.get(0).scheme());
+    assertEquals("Digest", challenges.get(0).scheme());
     assertEquals("myrealm", challenges.get(0).realm());
     Map<String, String> expectedAuthParams = new LinkedHashMap<>();
     expectedAuthParams.put("realm", "myrealm");
@@ -481,7 +481,7 @@ public final class HeadersTest {
         .build();
     List<Challenge> challenges = HttpHeaders.parseChallenges(headers, "WWW-Authenticate");
     assertEquals(1, challenges.size());
-    assertEquals("digest", challenges.get(0).scheme());
+    assertEquals("Digest", challenges.get(0).scheme());
     assertNull(challenges.get(0).realm());
     Map<String, String> expectedAuthParams = new LinkedHashMap<>();
     expectedAuthParams.put("underrealm", "myrealm");
@@ -498,7 +498,7 @@ public final class HeadersTest {
         .build();
     List<Challenge> challenges = HttpHeaders.parseChallenges(headers, "WWW-Authenticate");
     assertEquals(1, challenges.size());
-    assertEquals("digest", challenges.get(0).scheme());
+    assertEquals("Digest", challenges.get(0).scheme());
     assertEquals("myrealm", challenges.get(0).realm());
     Map<String, String> expectedAuthParams = new LinkedHashMap<>();
     expectedAuthParams.put("realm", "myrealm");
@@ -515,7 +515,7 @@ public final class HeadersTest {
         .build();
     List<Challenge> challenges = HttpHeaders.parseChallenges(headers, "WWW-Authenticate");
     assertEquals(1, challenges.size());
-    assertEquals("digest", challenges.get(0).scheme());
+    assertEquals("Digest", challenges.get(0).scheme());
     assertEquals("myrealm", challenges.get(0).realm());
     Map<String, String> expectedAuthParams = new LinkedHashMap<>();
     expectedAuthParams.put("realm", "myrealm");
@@ -532,7 +532,7 @@ public final class HeadersTest {
         .build();
     List<Challenge> challenges = HttpHeaders.parseChallenges(headers, "WWW-Authenticate");
     assertEquals(1, challenges.size());
-    assertEquals("digest", challenges.get(0).scheme());
+    assertEquals("DiGeSt", challenges.get(0).scheme());
     assertEquals("myrealm", challenges.get(0).realm());
     Map<String, String> expectedAuthParams = new LinkedHashMap<>();
     expectedAuthParams.put("realm", "myrealm");
@@ -550,7 +550,7 @@ public final class HeadersTest {
         .build();
     List<Challenge> challenges = HttpHeaders.parseChallenges(headers, "WWW-Authenticate");
     assertEquals(1, challenges.size());
-    assertEquals("digest", challenges.get(0).scheme());
+    assertEquals("DIgEsT", challenges.get(0).scheme());
     assertEquals("myrealm", challenges.get(0).realm());
     Map<String, String> expectedAuthParams = new LinkedHashMap<>();
     expectedAuthParams.put("realm", "myrealm");
@@ -565,7 +565,7 @@ public final class HeadersTest {
         .add("WWW-Authenticate", "Digest realm=myrealm").build();
     List<Challenge> challenges = HttpHeaders.parseChallenges(headers, "WWW-Authenticate");
     assertEquals(1, challenges.size());
-    assertEquals("digest", challenges.get(0).scheme());
+    assertEquals("Digest", challenges.get(0).scheme());
     assertEquals("myrealm", challenges.get(0).realm());
     assertEquals(singletonMap("realm", "myrealm"), challenges.get(0).authParams());
   }
@@ -576,7 +576,7 @@ public final class HeadersTest {
         .add("WWW-Authenticate", "Digest").build();
     List<Challenge> challenges = HttpHeaders.parseChallenges(headers, "WWW-Authenticate");
     assertEquals(1, challenges.size());
-    assertEquals("digest", challenges.get(0).scheme());
+    assertEquals("Digest", challenges.get(0).scheme());
     assertNull(challenges.get(0).realm());
     assertEquals(emptyMap(), challenges.get(0).authParams());
   }
diff --git a/okhttp/src/main/java/okhttp3/Challenge.java b/okhttp/src/main/java/okhttp3/Challenge.java
index 5acaa907d..bff1cb830 100644
--- a/okhttp/src/main/java/okhttp3/Challenge.java
+++ b/okhttp/src/main/java/okhttp3/Challenge.java
@@ -34,7 +34,7 @@ public final class Challenge {
   public Challenge(String scheme, Map<String, String> authParams) {
     if (scheme == null) throw new NullPointerException("scheme == null");
     if (authParams == null) throw new NullPointerException("authParams == null");
-    this.scheme = scheme.toLowerCase(US);
+    this.scheme = scheme;
     Map<String, String> newAuthParams = new LinkedHashMap<>();
     for (Entry<String, String> authParam : authParams.entrySet()) {
       String key = (authParam.getKey() == null) ? null : authParam.getKey().toLowerCase(US);
@@ -46,7 +46,7 @@ public final class Challenge {
   public Challenge(String scheme, String realm) {
     if (scheme == null) throw new NullPointerException("scheme == null");
     if (realm == null) throw new NullPointerException("realm == null");
-    this.scheme = scheme.toLowerCase(US);
+    this.scheme = scheme;
     this.authParams = singletonMap("realm", realm);
   }
 
@@ -58,15 +58,14 @@ public final class Challenge {
     return new Challenge(scheme, authParams);
   }
 
-  /** Returns the authentication scheme in lowercase, like {@code basic}. */
+  /** Returns the authentication scheme, like {@code Basic}. */
   public String scheme() {
     return scheme;
   }
 
   /**
-   * Returns the auth params, including {@code realm} and {@code charset} if present,
-   * but as {@code String}s. The keys are all lowercase, as the auth param names
-   * are to be treated case insensitively anyway.
+   * Returns the auth params, including {@code realm} and {@code charset} if present, but as
+   * strings. The map's keys are lowercase and should be treated case-insensitively.
    */
   public Map<String, String> authParams() {
     return authParams;