diff --git a/src/util.cc b/src/util.cc
index 5c7d320d..8fbb66d8 100644
--- a/src/util.cc
+++ b/src/util.cc
@@ -81,6 +81,7 @@
 #include "Logger.h"
 #include "Option.h"
 #include "DownloadContext.h"
+#include "uri.h"
 
 #ifdef ENABLE_MESSAGE_DIGEST
 # include "MessageDigest.h"
@@ -1583,6 +1584,31 @@ std::string safeStrerror(int errNum)
   return makeString(strerror(errNum));
 }
 
+std::string joinUri(const std::string& baseUri, const std::string& uri)
+{
+  uri::UriStruct us;
+  if(uri::parse(us, uri)) {
+    return uri;
+  } else {
+    uri::UriStruct bus;
+    if(!uri::parse(bus, baseUri)) {
+      return uri;
+    }
+    if(util::startsWith(uri, "/")) {
+      bus.dir.clear();
+    }
+    bus.file.clear();
+    bus.query.clear();
+    std::string newUri = construct(bus);
+    if(util::startsWith(uri, "/")) {
+      newUri += uri.substr(1);
+    } else {
+      newUri += uri;
+    }
+    return newUri;
+  }
+}
+
 } // namespace util
 
 } // namespace aria2
diff --git a/src/util.h b/src/util.h
index 939dc2b7..b632433a 100644
--- a/src/util.h
+++ b/src/util.h
@@ -324,6 +324,8 @@ std::string joinPath(InputIterator first, InputIterator last)
   return strjoin(elements.begin(), elements.end(), "/");
 }
 
+std::string joinUri(const std::string& baseUri, const std::string& uri);
+
 // Parses INDEX=PATH format string. INDEX must be an unsigned
 // integer.
 std::map<size_t, std::string>::value_type
diff --git a/test/UtilTest.cc b/test/UtilTest.cc
index 02e884f1..48f5d6fa 100644
--- a/test/UtilTest.cc
+++ b/test/UtilTest.cc
@@ -71,6 +71,7 @@ class UtilTest:public CppUnit::TestFixture {
   CPPUNIT_TEST(testGetCidrPrefix);
   CPPUNIT_TEST(testInSameCidrBlock);
   CPPUNIT_TEST(testIsUtf8String);
+  CPPUNIT_TEST(testJoinUri);
   CPPUNIT_TEST_SUITE_END();
 private:
 
@@ -130,6 +131,7 @@ public:
   void testGetCidrPrefix();
   void testInSameCidrBlock();
   void testIsUtf8String();
+  void testJoinUri();
 };
 
 
@@ -1247,4 +1249,25 @@ void UtilTest::testIsUtf8String()
   CPPUNIT_ASSERT(!util::isUtf8(util::fromHex("00")));
 }
 
+void UtilTest::testJoinUri()
+{
+  CPPUNIT_ASSERT_EQUAL(std::string("http://host/dir/file"),
+                       util::joinUri("http://base/d/f",
+                                     "http://host/dir/file"));
+  CPPUNIT_ASSERT_EQUAL(std::string("http://base/dir/file"),
+                       util::joinUri("http://base/d/f",
+                                     "/dir/file"));
+  CPPUNIT_ASSERT_EQUAL(std::string("http://base/d/dir/file"),
+                       util::joinUri("http://base/d/f",
+                                     "dir/file"));
+  CPPUNIT_ASSERT_EQUAL(std::string("http://base/d/"),
+                       util::joinUri("http://base/d/f",
+                                     ""));
+  CPPUNIT_ASSERT_EQUAL(std::string("http://base/d/dir/file?q=k"),
+                       util::joinUri("http://base/d/f",
+                                     "dir/file?q=k"));
+  CPPUNIT_ASSERT_EQUAL(std::string("dir/file"),
+                       util::joinUri("baduri", "dir/file"));
+}
+
 } // namespace aria2