diff --git a/netwerk/base/src/nsStandardURL.cpp b/netwerk/base/src/nsStandardURL.cpp
index 45c69871b205..b7c12f4c3364 100644
--- a/netwerk/base/src/nsStandardURL.cpp
+++ b/netwerk/base/src/nsStandardURL.cpp
@@ -560,6 +560,11 @@ nsStandardURL::BuildNormalizedSpec(const char *spec)
             LOG(("adding leading slash to path\n"));
             leadingSlash = 1;
             buf[i++] = '/';
+            // basename must exist, even if empty (bugs 113508, 429347)
+            if (mBasename.mLen == -1) {
+                mBasename.mPos = i;
+                mBasename.mLen = 0;
+            }
         }
 
         // record corrected (file)path starting position
diff --git a/netwerk/test/unit/test_bug429347.js b/netwerk/test/unit/test_bug429347.js
new file mode 100644
index 000000000000..166358149841
--- /dev/null
+++ b/netwerk/test/unit/test_bug429347.js
@@ -0,0 +1,36 @@
+const Cc = Components.classes;
+const Ci = Components.interfaces;
+const Cr = Components.results;
+
+function run_test() {
+  var ios = Cc["@mozilla.org/network/io-service;1"].
+    getService(Ci.nsIIOService);
+
+  var uri1 = ios.newURI("http://example.com#bar", null, null);
+  var uri2 = ios.newURI("http://example.com/#bar", null, null);
+  do_check_true(uri1.equals(uri2));
+
+  uri1.spec = "http://example.com?bar";
+  uri2.spec = "http://example.com/?bar";
+  do_check_true(uri1.equals(uri2));
+
+  uri1.spec = "http://example.com;bar";
+  uri2.spec = "http://example.com/;bar";
+  do_check_true(uri1.equals(uri2));
+
+  uri1.spec = "http://example.com#";
+  uri2.spec = "http://example.com/#";
+  do_check_true(uri1.equals(uri2));
+
+  uri1.spec = "http://example.com?";
+  uri2.spec = "http://example.com/?";
+  do_check_true(uri1.equals(uri2));
+
+  uri1.spec = "http://example.com;";
+  uri2.spec = "http://example.com/;";
+  do_check_true(uri1.equals(uri2));
+
+  uri1.spec = "http://example.com";
+  uri2.spec = "http://example.com/";
+  do_check_true(uri1.equals(uri2));
+}
diff --git a/netwerk/test/unit/test_standardurl.js b/netwerk/test/unit/test_standardurl.js
index 5d0ae21f06c4..2684d7342ba5 100644
--- a/netwerk/test/unit/test_standardurl.js
+++ b/netwerk/test/unit/test_standardurl.js
@@ -68,8 +68,7 @@ function test_setQuery()
     [
      ["http://example.com", "http://example.com/?foo"],
      ["http://example.com/bar", "http://example.com/bar?foo"],
-     /* Can't test the path-less thing because of bug 429347 */
-     /* ["http://example.com#bar", "http://example.com/?foo#bar"], */
+     ["http://example.com#bar", "http://example.com/?foo#bar"],
      ["http://example.com/#bar", "http://example.com/?foo#bar"],
      ["http://example.com/?longerthanfoo#bar", "http://example.com/?foo#bar"],
      ["http://example.com/?longerthanfoo", "http://example.com/?foo"],