diff --git a/okhttp-tests/src/test/java/okhttp3/HttpUrlTest.java b/okhttp-tests/src/test/java/okhttp3/HttpUrlTest.java
index 6589d5850c9d..e780d8bd9b9d 100644
--- a/okhttp-tests/src/test/java/okhttp3/HttpUrlTest.java
+++ b/okhttp-tests/src/test/java/okhttp3/HttpUrlTest.java
@@ -779,9 +779,9 @@ HttpUrl parse(String url) {
   @Test public void incompleteBuilderToString() {
     assertEquals("https:///path",
         new HttpUrl.Builder().scheme("https").encodedPath("/path").toString());
-    assertEquals("://host.com/path",
+    assertEquals("//host.com/path",
         new HttpUrl.Builder().host("host.com").encodedPath("/path").toString());
-    assertEquals("://host.com:8080/path",
+    assertEquals("//host.com:8080/path",
         new HttpUrl.Builder().host("host.com").encodedPath("/path").port(8080).toString());
   }
 
diff --git a/okhttp/src/main/java/okhttp3/HttpUrl.java b/okhttp/src/main/java/okhttp3/HttpUrl.java
index 528d1cc46a58..9ca007cefd37 100644
--- a/okhttp/src/main/java/okhttp3/HttpUrl.java
+++ b/okhttp/src/main/java/okhttp3/HttpUrl.java
@@ -1260,8 +1260,10 @@ public HttpUrl build() {
       StringBuilder result = new StringBuilder();
       if (scheme != null) {
         result.append(scheme);
+        result.append("://");
+      } else {
+        result.append("//");
       }
-      result.append("://");
 
       if (!encodedUsername.isEmpty() || !encodedPassword.isEmpty()) {
         result.append(encodedUsername);