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 b281069f5..66288a198 100644
--- a/okhttp-tests/src/test/java/com/squareup/okhttp/HttpUrlTest.java
+++ b/okhttp-tests/src/test/java/com/squareup/okhttp/HttpUrlTest.java
@@ -17,8 +17,10 @@ package com.squareup.okhttp;
 
 import com.squareup.okhttp.UrlComponentEncodingTester.Component;
 import com.squareup.okhttp.UrlComponentEncodingTester.Encoding;
+import java.net.MalformedURLException;
 import java.net.URI;
 import java.net.URL;
+import java.net.UnknownHostException;
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.LinkedHashSet;
@@ -949,6 +951,27 @@ public final class HttpUrlTest {
     assertEquals(null, HttpUrl.get(uri));
   }
 
+  @Test public void fromJavaNetUrl_checked() throws Exception {
+    HttpUrl httpUrl = HttpUrl.getChecked("http://username:password@host/path?query#fragment");
+    assertEquals("http://username:password@host/path?query#fragment", httpUrl.toString());
+  }
+
+  @Test public void fromJavaNetUrlUnsupportedScheme_checked() throws Exception {
+    try {
+      HttpUrl.getChecked("mailto:user@example.com");
+      fail();
+    } catch (MalformedURLException e) {
+    }
+  }
+
+  @Test public void fromJavaNetUrlBadHost_checked() throws Exception {
+    try {
+      HttpUrl.getChecked("http://hostw ithspace/");
+      fail();
+    } catch (UnknownHostException expected) {
+    }
+  }
+
   @Test public void composeQueryWithComponents() throws Exception {
     HttpUrl base = HttpUrl.parse("http://host/");
     HttpUrl url = base.newBuilder().addQueryParameter("a+=& b", "c+=& d").build();
diff --git a/okhttp-tests/src/test/java/com/squareup/okhttp/URLConnectionTest.java b/okhttp-tests/src/test/java/com/squareup/okhttp/URLConnectionTest.java
index 2ea599707..65c1c057a 100644
--- a/okhttp-tests/src/test/java/com/squareup/okhttp/URLConnectionTest.java
+++ b/okhttp-tests/src/test/java/com/squareup/okhttp/URLConnectionTest.java
@@ -3178,6 +3178,37 @@ public final class URLConnectionTest {
     assertContent("abc", client.open(server.getUrl("/")));
   }
 
+  @Test public void urlWithSpaceInHost() throws Exception {
+    URLConnection urlConnection = client.open(new URL("http://and roid.com/"));
+    try {
+      urlConnection.getInputStream();
+      fail();
+    } catch (UnknownHostException expected) {
+    }
+  }
+
+  @Test public void urlWithSpaceInHostViaHttpProxy() throws Exception {
+    server.enqueue(new MockResponse());
+    URLConnection urlConnection =
+        client.open(new URL("http://and roid.com/"), server.toProxyAddress());
+
+    try {
+      // This test is to check that a NullPointerException is not thrown.
+      urlConnection.getInputStream();
+      fail(); // the RI makes a bogus proxy request for "GET http://and roid.com/ HTTP/1.1"
+    } catch (UnknownHostException expected) {
+    }
+  }
+
+  @Test public void urlHostWithNul() throws Exception {
+    URLConnection urlConnection = client.open(new URL("http://host\u0000/"));
+    try {
+      urlConnection.getInputStream();
+      fail();
+    } catch (UnknownHostException expected) {
+    }
+  }
+
   /** Returns a gzipped copy of {@code bytes}. */
   public Buffer gzip(String data) throws IOException {
     Buffer result = new Buffer();
diff --git a/okhttp-urlconnection/src/main/java/com/squareup/okhttp/internal/huc/HttpURLConnectionImpl.java b/okhttp-urlconnection/src/main/java/com/squareup/okhttp/internal/huc/HttpURLConnectionImpl.java
index 8db26d75f..1cddd3ecb 100644
--- a/okhttp-urlconnection/src/main/java/com/squareup/okhttp/internal/huc/HttpURLConnectionImpl.java
+++ b/okhttp-urlconnection/src/main/java/com/squareup/okhttp/internal/huc/HttpURLConnectionImpl.java
@@ -46,10 +46,12 @@ import java.io.OutputStream;
 import java.net.HttpRetryException;
 import java.net.HttpURLConnection;
 import java.net.InetSocketAddress;
+import java.net.MalformedURLException;
 import java.net.ProtocolException;
 import java.net.Proxy;
 import java.net.SocketPermission;
 import java.net.URL;
+import java.net.UnknownHostException;
 import java.security.Permission;
 import java.util.ArrayList;
 import java.util.Arrays;
@@ -321,14 +323,16 @@ public class HttpURLConnectionImpl extends HttpURLConnection {
     }
   }
 
-  private HttpEngine newHttpEngine(String method, Connection connection,
-      RetryableSink requestBody, Response priorResponse) {
+  private HttpEngine newHttpEngine(String method, Connection connection, RetryableSink requestBody,
+      Response priorResponse) throws MalformedURLException, UnknownHostException {
     // OkHttp's Call API requires a placeholder body; the real body will be streamed separately.
     RequestBody placeholderBody = HttpMethod.requiresRequestBody(method)
         ? EMPTY_REQUEST_BODY
         : null;
+    URL url = getURL();
+    HttpUrl httpUrl = Internal.instance.getHttpUrlChecked(url.toString());
     Request.Builder builder = new Request.Builder()
-        .url(getURL())
+        .url(httpUrl)
         .method(method, placeholderBody);
     Headers headers = requestHeaders.build();
     for (int i = 0, size = headers.size(); i < size; i++) {
diff --git a/okhttp/src/main/java/com/squareup/okhttp/HttpUrl.java b/okhttp/src/main/java/com/squareup/okhttp/HttpUrl.java
index dc8c7f2e0..2f0abfa1f 100644
--- a/okhttp/src/main/java/com/squareup/okhttp/HttpUrl.java
+++ b/okhttp/src/main/java/com/squareup/okhttp/HttpUrl.java
@@ -561,7 +561,9 @@ public final class HttpUrl {
 
   /** Returns the URL that would be retrieved by following {@code link} from this URL. */
   public HttpUrl resolve(String link) {
-    return new Builder().parse(this, link);
+    Builder builder = new Builder();
+    Builder.ParseResult result = builder.parse(this, link);
+    return result == Builder.ParseResult.SUCCESS ? builder.build() : null;
   }
 
   public Builder newBuilder() {
@@ -584,11 +586,13 @@ public final class HttpUrl {
   }
 
   /**
-   * Returns a new {@code OkUrl} representing {@code url} if it is a well-formed HTTP or HTTPS URL,
-   * or null if it isn't.
+   * Returns a new {@code HttpUrl} representing {@code url} if it is a well-formed HTTP or HTTPS
+   * URL, or null if it isn't.
    */
   public static HttpUrl parse(String url) {
-    return new Builder().parse(null, url);
+    Builder builder = new Builder();
+    Builder.ParseResult result = builder.parse(null, url);
+    return result == Builder.ParseResult.SUCCESS ? builder.build() : null;
   }
 
   /**
@@ -599,6 +603,29 @@ public final class HttpUrl {
     return parse(url.toString());
   }
 
+  /**
+   * Returns a new {@code HttpUrl} representing {@code url} if it is a well-formed HTTP or HTTPS
+   * URL, or throws an exception if it isn't.
+   *
+   * @throws MalformedURLException if there was a non-host related URL issue
+   * @throws UnknownHostException if the host was invalid
+   */
+  static HttpUrl getChecked(String url) throws MalformedURLException, UnknownHostException {
+    Builder builder = new Builder();
+    Builder.ParseResult result = builder.parse(null, url);
+    switch (result) {
+      case SUCCESS:
+        return builder.build();
+      case INVALID_HOST:
+        throw new UnknownHostException("Invalid host: " + url);
+      case UNSUPPORTED_SCHEME:
+      case MISSING_SCHEME:
+      case INVALID_PORT:
+      default:
+        throw new MalformedURLException("Invalid URL: " + result + " for " + url);
+    }
+  }
+
   public static HttpUrl get(URI uri) {
     return parse(uri.toString());
   }
@@ -883,7 +910,15 @@ public final class HttpUrl {
       return result.toString();
     }
 
-    HttpUrl parse(HttpUrl base, String input) {
+    enum ParseResult {
+      SUCCESS,
+      MISSING_SCHEME,
+      UNSUPPORTED_SCHEME,
+      INVALID_PORT,
+      INVALID_HOST,
+    }
+
+    ParseResult parse(HttpUrl base, String input) {
       int pos = skipLeadingAsciiWhitespace(input, 0, input.length());
       int limit = skipTrailingAsciiWhitespace(input, pos, input.length());
 
@@ -897,12 +932,12 @@ public final class HttpUrl {
           this.scheme = "http";
           pos += "http:".length();
         } else {
-          return null; // Not an HTTP scheme.
+          return ParseResult.UNSUPPORTED_SCHEME; // Not an HTTP scheme.
         }
       } else if (base != null) {
         this.scheme = base.scheme;
       } else {
-        return null; // No scheme.
+        return ParseResult.MISSING_SCHEME; // No scheme.
       }
 
       // Authority.
@@ -960,12 +995,12 @@ public final class HttpUrl {
               if (portColonOffset + 1 < componentDelimiterOffset) {
                 this.host = canonicalizeHost(input, pos, portColonOffset);
                 this.port = parsePort(input, portColonOffset + 1, componentDelimiterOffset);
-                if (this.port == -1) return null; // Invalid port.
+                if (this.port == -1) return ParseResult.INVALID_PORT; // Invalid port.
               } else {
                 this.host = canonicalizeHost(input, pos, portColonOffset);
                 this.port = defaultPort(this.scheme);
               }
-              if (this.host == null) return null; // Invalid host.
+              if (this.host == null) return ParseResult.INVALID_HOST; // Invalid host.
               pos = componentDelimiterOffset;
               break authority;
           }
@@ -1002,7 +1037,7 @@ public final class HttpUrl {
             input, pos + 1, limit, FRAGMENT_ENCODE_SET, true, false);
       }
 
-      return build();
+      return ParseResult.SUCCESS;
     }
 
     private void resolvePath(String input, int pos, int limit) {
diff --git a/okhttp/src/main/java/com/squareup/okhttp/OkHttpClient.java b/okhttp/src/main/java/com/squareup/okhttp/OkHttpClient.java
index 1ef79b0f6..4ed8000a6 100644
--- a/okhttp/src/main/java/com/squareup/okhttp/OkHttpClient.java
+++ b/okhttp/src/main/java/com/squareup/okhttp/OkHttpClient.java
@@ -27,9 +27,11 @@ import com.squareup.okhttp.internal.http.Transport;
 import com.squareup.okhttp.internal.tls.OkHostnameVerifier;
 import java.io.IOException;
 import java.net.CookieHandler;
+import java.net.MalformedURLException;
 import java.net.Proxy;
 import java.net.ProxySelector;
 import java.net.URLConnection;
+import java.net.UnknownHostException;
 import java.security.GeneralSecurityException;
 import java.util.ArrayList;
 import java.util.List;
@@ -157,6 +159,11 @@ public class OkHttpClient implements Cloneable {
       public void apply(ConnectionSpec tlsConfiguration, SSLSocket sslSocket, boolean isFallback) {
         tlsConfiguration.apply(sslSocket, isFallback);
       }
+
+      @Override public HttpUrl getHttpUrlChecked(String url)
+          throws MalformedURLException, UnknownHostException {
+        return HttpUrl.getChecked(url);
+      }
     };
   }
 
diff --git a/okhttp/src/main/java/com/squareup/okhttp/internal/Internal.java b/okhttp/src/main/java/com/squareup/okhttp/internal/Internal.java
index 1e583ba1b..21bcbf5c3 100644
--- a/okhttp/src/main/java/com/squareup/okhttp/internal/Internal.java
+++ b/okhttp/src/main/java/com/squareup/okhttp/internal/Internal.java
@@ -21,6 +21,7 @@ import com.squareup.okhttp.Connection;
 import com.squareup.okhttp.ConnectionPool;
 import com.squareup.okhttp.ConnectionSpec;
 import com.squareup.okhttp.Headers;
+import com.squareup.okhttp.HttpUrl;
 import com.squareup.okhttp.OkHttpClient;
 import com.squareup.okhttp.Protocol;
 import com.squareup.okhttp.Request;
@@ -28,6 +29,8 @@ import com.squareup.okhttp.internal.http.HttpEngine;
 import com.squareup.okhttp.internal.http.RouteException;
 import com.squareup.okhttp.internal.http.Transport;
 import java.io.IOException;
+import java.net.MalformedURLException;
+import java.net.UnknownHostException;
 import java.util.logging.Logger;
 import javax.net.ssl.SSLSocket;
 import okio.BufferedSink;
@@ -85,6 +88,9 @@ public abstract class Internal {
   public abstract void apply(ConnectionSpec tlsConfiguration, SSLSocket sslSocket,
       boolean isFallback);
 
+  public abstract HttpUrl getHttpUrlChecked(String url)
+      throws MalformedURLException, UnknownHostException;
+
   // TODO delete the following when web sockets move into the main package.
   public abstract void callEnqueue(Call call, Callback responseCallback, boolean forWebSocket);
   public abstract void callEngineReleaseConnection(Call call) throws IOException;