diff --git a/netwerk/base/Predictor.cpp b/netwerk/base/Predictor.cpp
index e5982655e254..7b89fdfa8535 100644
--- a/netwerk/base/Predictor.cpp
+++ b/netwerk/base/Predictor.cpp
@@ -1311,9 +1311,9 @@ Predictor::CalculatePredictions(nsICacheEntry *entry, nsIURI *referrer,
     const char *key = keysToOperateOn[i].BeginReading();
     const char *value = valuesToOperateOn[i].BeginReading();
 
-    nsCOMPtr<nsIURI> uri;
+    nsCString uri;
     uint32_t hitCount, lastHit, flags;
-    if (!ParseMetaDataEntry(key, value, getter_AddRefs(uri), hitCount, lastHit, flags)) {
+    if (!ParseMetaDataEntry(key, value, uri, hitCount, lastHit, flags)) {
       // This failed, get rid of it so we don't waste space
       entry->SetMetaDataElement(key, nullptr);
       continue;
@@ -1351,24 +1351,42 @@ Predictor::CalculatePredictions(nsICacheEntry *entry, nsIURI *referrer,
 // (Maybe) adds a predictive action to the prediction runner, based on our
 // calculated confidence for the subresource in question.
 void
-Predictor::SetupPrediction(int32_t confidence, uint32_t flags, nsIURI *uri)
+Predictor::SetupPrediction(int32_t confidence, uint32_t flags, const nsCString &uri)
 {
   MOZ_ASSERT(NS_IsMainThread());
 
-  nsAutoCString uriStr;
-  uri->GetAsciiSpec(uriStr);
+  nsresult rv = NS_OK;
   PREDICTOR_LOG(("SetupPrediction mEnablePrefetch=%d mPrefetchMinConfidence=%d "
                  "mPreconnectMinConfidence=%d mPreresolveMinConfidence=%d "
                  "flags=%d confidence=%d uri=%s", mEnablePrefetch,
                  mPrefetchMinConfidence, mPreconnectMinConfidence,
-                 mPreresolveMinConfidence, flags, confidence, uriStr.get()));
+                 mPreresolveMinConfidence, flags, confidence, uri.get()));
   if (mEnablePrefetch && (flags & FLAG_PREFETCHABLE) &&
       (mPrefetchRollingLoadCount || (confidence >= mPrefetchMinConfidence))) {
-    mPrefetches.AppendElement(uri);
+    nsCOMPtr<nsIURI> prefetchURI;
+    rv = NS_NewURI(getter_AddRefs(prefetchURI), uri, nullptr, nullptr,
+                   mIOService);
+    if (NS_SUCCEEDED(rv)) {
+      mPrefetches.AppendElement(prefetchURI);
+    }
   } else if (confidence >= mPreconnectMinConfidence) {
-    mPreconnects.AppendElement(uri);
+    nsCOMPtr<nsIURI> preconnectURI;
+    rv = NS_NewURI(getter_AddRefs(preconnectURI), uri, nullptr, nullptr,
+                   mIOService);
+    if (NS_SUCCEEDED(rv)) {
+      mPreconnects.AppendElement(preconnectURI);
+    }
   } else if (confidence >= mPreresolveMinConfidence) {
-    mPreresolves.AppendElement(uri);
+    nsCOMPtr<nsIURI> preresolveURI;
+    rv = NS_NewURI(getter_AddRefs(preresolveURI), uri, nullptr, nullptr,
+                   mIOService);
+    if (NS_SUCCEEDED(rv)) {
+      mPreresolves.AppendElement(preresolveURI);
+    }
+  }
+
+  if (NS_FAILED(rv)) {
+    PREDICTOR_LOG(("    NS_NewURI returned 0x%" PRIx32, static_cast<uint32_t>(rv)));
   }
 }
 
@@ -1754,9 +1772,9 @@ Predictor::LearnInternal(PredictorLearnReason reason, nsICacheEntry *entry,
           const char *key = keysToOperateOn[i].BeginReading();
           const char *value = valuesToOperateOn[i].BeginReading();
 
-          nsCOMPtr<nsIURI> uri;
+          nsCString uri;
           uint32_t hitCount, lastHit, flags;
-          if (!ParseMetaDataEntry(nullptr, value, nullptr, hitCount, lastHit, flags)) {
+          if (!ParseMetaDataEntry(key, value, uri, hitCount, lastHit, flags)) {
             // This failed, get rid of it so we don't waste space
             entry->SetMetaDataElement(key, nullptr);
             continue;
@@ -1796,9 +1814,9 @@ Predictor::SpaceCleaner::OnMetaDataElement(const char *key, const char *value)
     return NS_OK;
   }
 
+  nsCString uri;
   uint32_t hitCount, lastHit, flags;
-  bool ok = mPredictor->ParseMetaDataEntry(nullptr, value, nullptr,
-                                           hitCount, lastHit, flags);
+  bool ok = mPredictor->ParseMetaDataEntry(key, value, uri, hitCount, lastHit, flags);
 
   if (!ok) {
     // Couldn't parse this one, just get rid of it
@@ -1808,7 +1826,6 @@ Predictor::SpaceCleaner::OnMetaDataElement(const char *key, const char *value)
     return NS_OK;
   }
 
-  nsCString uri(key + (sizeof(META_DATA_PREFIX) - 1));
   uint32_t uriLength = uri.Length();
   if (uriLength > mPredictor->mMaxURILength) {
     // Default to getting rid of URIs that are too long and were put in before
@@ -1875,8 +1892,9 @@ Predictor::LearnForSubresource(nsICacheEntry *entry, nsIURI *targetURI)
 
   uint32_t hitCount, lastHit, flags;
   bool isNewResource = (NS_FAILED(rv) ||
-                        !ParseMetaDataEntry(nullptr, value.BeginReading(),
-                                            nullptr, hitCount, lastHit, flags));
+                        !ParseMetaDataEntry(key.BeginReading(),
+                                            value.BeginReading(), uri,
+                                            hitCount, lastHit, flags));
 
   int32_t resourceCount = 0;
   if (isNewResource) {
@@ -1968,7 +1986,7 @@ Predictor::LearnForStartup(nsICacheEntry *entry, nsIURI *targetURI)
 }
 
 bool
-Predictor::ParseMetaDataEntry(const char *key, const char *value, nsIURI **uri,
+Predictor::ParseMetaDataEntry(const char *key, const char *value, nsCString &uri,
                               uint32_t &hitCount, uint32_t &lastHit,
                               uint32_t &flags)
 {
@@ -2018,12 +2036,10 @@ Predictor::ParseMetaDataEntry(const char *key, const char *value, nsIURI **uri,
 
   if (key) {
     const char *uriStart = key + (sizeof(META_DATA_PREFIX) - 1);
-    nsresult rv = NS_NewURI(uri, uriStart, nullptr, mIOService);
-    if (NS_FAILED(rv)) {
-      PREDICTOR_LOG(("    NS_NewURI returned 0x%" PRIX32, static_cast<uint32_t>(rv)));
-      return false;
-    }
+    uri.AssignASCII(uriStart);
     PREDICTOR_LOG(("    uri -> %s", uriStart));
+  } else {
+    uri.Truncate();
   }
 
   return true;
@@ -2677,7 +2693,14 @@ Predictor::CacheabilityAction::OnCacheEntryAvailable(nsICacheEntry *entry,
     return NS_OK;
   }
 
-  nsresult rv = entry->VisitMetaData(this);
+  nsCString strTargetURI;
+  nsresult rv = mTargetURI->GetAsciiSpec(strTargetURI);
+  if (NS_FAILED(rv)) {
+    PREDICTOR_LOG(("    GetAsciiSpec returned %" PRIx32, static_cast<uint32_t>(rv)));
+    return NS_OK;
+  }
+
+  rv = entry->VisitMetaData(this);
   if (NS_FAILED(rv)) {
     PREDICTOR_LOG(("    VisitMetaData returned %" PRIx32, static_cast<uint32_t>(rv)));
     return NS_OK;
@@ -2697,17 +2720,16 @@ Predictor::CacheabilityAction::OnCacheEntryAvailable(nsICacheEntry *entry,
   for (size_t i = 0; i < keysToCheck.Length(); ++i) {
     const char *key = keysToCheck[i].BeginReading();
     const char *value = valuesToCheck[i].BeginReading();
-    nsCOMPtr<nsIURI> uri;
+    nsCString uri;
     uint32_t hitCount, lastHit, flags;
 
-    if (!mPredictor->ParseMetaDataEntry(key, value, getter_AddRefs(uri),
-                                        hitCount, lastHit, flags)) {
+    if (!mPredictor->ParseMetaDataEntry(key, value, uri, hitCount, lastHit,
+                                        flags)) {
       PREDICTOR_LOG(("    failed to parse key=%s value=%s", key, value));
       continue;
     }
 
-    bool eq = false;
-    if (NS_SUCCEEDED(uri->Equals(mTargetURI, &eq)) && eq) {
+    if (strTargetURI.Equals(uri)) {
       if (mHttpStatus == 200 && mMethod.EqualsLiteral("GET") && !hasQueryString) {
         PREDICTOR_LOG(("    marking %s cacheable", key));
         flags |= FLAG_PREFETCHABLE;
diff --git a/netwerk/base/Predictor.h b/netwerk/base/Predictor.h
index 157c58969ca5..beca80ace852 100644
--- a/netwerk/base/Predictor.h
+++ b/netwerk/base/Predictor.h
@@ -330,8 +330,8 @@ private:
   // Used to prepare any necessary prediction for a resource on a page
   //   * confidence - value calculated by CalculateConfidence for this resource
   //   * flags - the flags taken from the resource
-  //   * uri - the URI of the resource
-  void SetupPrediction(int32_t confidence, uint32_t flags, nsIURI *uri);
+  //   * uri - the ascii spec of the URI of the resource
+  void SetupPrediction(int32_t confidence, uint32_t flags, const nsCString &uri);
 
   // Used to kick off a prefetch from RunPredictions if necessary
   //   * uri - the URI to prefetch
@@ -409,11 +409,11 @@ private:
   // Used to parse the data we store in cache metadata
   //   * key - the cache metadata key
   //   * value - the cache metadata value
-  //   * uri - (out) the URI this metadata entry was about
+  //   * uri - (out) the ascii spec of the URI this metadata entry was about
   //   * hitCount - (out) the number of times this URI has been seen
   //   * lastHit - (out) timestamp of the last time this URI was seen
   //   * flags - (out) flags for this metadata entry
-  bool ParseMetaDataEntry(const char *key, const char *value, nsIURI **uri,
+  bool ParseMetaDataEntry(const char *key, const char *value, nsCString &uri,
                           uint32_t &hitCount, uint32_t &lastHit,
                           uint32_t &flags);