diff --git a/okhttp-tests/src/test/java/com/squareup/okhttp/HttpUrlTest.java b/okhttp-tests/src/test/java/com/squareup/okhttp/HttpUrlTest.java
index 9651bfb..10291f1 100644
--- a/okhttp-tests/src/test/java/com/squareup/okhttp/HttpUrlTest.java
+++ b/okhttp-tests/src/test/java/com/squareup/okhttp/HttpUrlTest.java
@@ -1172,4 +1172,24 @@
     assertEquals(urlString, url.newBuilder().build().toString());
     assertEquals("http://%6d%6D:%6d%6D@host/%6d%6D?%6d%6D", url.resolve("").toString());
   }
+
+  @Test public void clearFragment() throws Exception {
+    HttpUrl url = HttpUrl.parse("http://host/#fragment")
+        .newBuilder()
+        .fragment(null)
+        .build();
+    assertEquals("http://host/", url.toString());
+    assertEquals(null, url.fragment());
+    assertEquals(null, url.encodedFragment());
+  }
+
+  @Test public void clearEncodedFragment() throws Exception {
+    HttpUrl url = HttpUrl.parse("http://host/#fragment")
+        .newBuilder()
+        .encodedFragment(null)
+        .build();
+    assertEquals("http://host/", url.toString());
+    assertEquals(null, url.fragment());
+    assertEquals(null, url.encodedFragment());
+  }
 }
diff --git a/okhttp/src/main/java/com/squareup/okhttp/HttpUrl.java b/okhttp/src/main/java/com/squareup/okhttp/HttpUrl.java
index d56f525..a5b9876 100644
--- a/okhttp/src/main/java/com/squareup/okhttp/HttpUrl.java
+++ b/okhttp/src/main/java/com/squareup/okhttp/HttpUrl.java
@@ -867,14 +867,16 @@
     }
 
     public Builder fragment(String fragment) {
-      if (fragment == null) throw new IllegalArgumentException("fragment == null");
-      this.encodedFragment = canonicalize(fragment, FRAGMENT_ENCODE_SET, false, false);
+      this.encodedFragment = fragment != null
+          ? canonicalize(fragment, FRAGMENT_ENCODE_SET, false, false)
+          : null;
       return this;
     }
 
     public Builder encodedFragment(String encodedFragment) {
-      if (encodedFragment == null) throw new IllegalArgumentException("encodedFragment == null");
-      this.encodedFragment = canonicalize(encodedFragment, FRAGMENT_ENCODE_SET, true, false);
+      this.encodedFragment = encodedFragment != null
+          ? canonicalize(encodedFragment, FRAGMENT_ENCODE_SET, true, false)
+          : null;
       return this;
     }