diff --git a/netwerk/base/nsStandardURL.cpp b/netwerk/base/nsStandardURL.cpp
index 81b485502..1866c1037 100644
--- a/netwerk/base/nsStandardURL.cpp
+++ b/netwerk/base/nsStandardURL.cpp
@@ -2747,12 +2747,16 @@ nsStandardURL::SetFilePath(const nsACString &input)
 
         return SetSpec(spec);
     }
-    else if (mPath.mLen > 1) {
+
+    if (mPath.mLen > 1) {
         mSpec.Cut(mPath.mPos + 1, mFilepath.mLen - 1);
         // left shift query, and ref
         ShiftFromQuery(1 - mFilepath.mLen);
+        // One character for '/', and if we have a query or ref we add their
+        // length and one extra for each '?' or '#' characters
+        mPath.mLen = 1 + (mQuery.mLen >= 0 ? (mQuery.mLen + 1) : 0) +
+                     (mRef.mLen >= 0 ? (mRef.mLen + 1) : 0);
         // these contain only a '/'
-        mPath.mLen = 1;
         mDirectory.mLen = 1;
         mFilepath.mLen = 1;
         // these are no longer defined