diff --git a/parser/html/nsHtml5SpeculativeLoad.cpp b/parser/html/nsHtml5SpeculativeLoad.cpp
index 5dacb2e2753..733842b5815 100644
--- a/parser/html/nsHtml5SpeculativeLoad.cpp
+++ b/parser/html/nsHtml5SpeculativeLoad.cpp
@@ -57,6 +57,9 @@ void
 nsHtml5SpeculativeLoad::Perform(nsHtml5TreeOpExecutor* aExecutor)
 {
   switch (mOpCode) {
+    case eSpeculativeLoadBase:
+        aExecutor->SetSpeculationBase(mUrl);
+      break;
     case eSpeculativeLoadImage:
         aExecutor->PreloadImage(mUrl);
       break;
diff --git a/parser/html/nsHtml5SpeculativeLoad.h b/parser/html/nsHtml5SpeculativeLoad.h
index 17334f1d4b8..d6c8c0ba87e 100644
--- a/parser/html/nsHtml5SpeculativeLoad.h
+++ b/parser/html/nsHtml5SpeculativeLoad.h
@@ -46,6 +46,7 @@ enum eHtml5SpeculativeLoad {
 #ifdef DEBUG
   eSpeculativeLoadUninitialized,
 #endif
+  eSpeculativeLoadBase,
   eSpeculativeLoadImage,
   eSpeculativeLoadScript,
   eSpeculativeLoadStyle,
@@ -57,6 +58,13 @@ class nsHtml5SpeculativeLoad {
     nsHtml5SpeculativeLoad();
     ~nsHtml5SpeculativeLoad();
     
+    inline void InitBase(const nsAString& aUrl) {
+      NS_PRECONDITION(mOpCode == eSpeculativeLoadUninitialized,
+                      "Trying to reinitialize a speculative load!");
+      mOpCode = eSpeculativeLoadBase;
+      mUrl.Assign(aUrl);
+    }
+
     inline void InitImage(const nsAString& aUrl) {
       NS_PRECONDITION(mOpCode == eSpeculativeLoadUninitialized,
                       "Trying to reinitialize a speculative load!");
diff --git a/parser/html/nsHtml5TreeBuilderCppSupplement.h b/parser/html/nsHtml5TreeBuilderCppSupplement.h
index 9699fb3bdb4..1f4311eb8da 100644
--- a/parser/html/nsHtml5TreeBuilderCppSupplement.h
+++ b/parser/html/nsHtml5TreeBuilderCppSupplement.h
@@ -149,6 +149,14 @@ nsHtml5TreeBuilder::createElement(PRInt32 aNamespace, nsIAtom* aName, nsHtml5Htm
           if (url) {
             mSpeculativeLoadQueue.AppendElement()->InitManifest(*url);
           }
+        } else if (nsHtml5Atoms::base == aName &&
+            (mode == NS_HTML5TREE_BUILDER_IN_HEAD ||
+             mode == NS_HTML5TREE_BUILDER_AFTER_HEAD)) {
+          nsString* url =
+              aAttributes->getValue(nsHtml5AttributeName::ATTR_HREF);
+          if (url) {
+            mSpeculativeLoadQueue.AppendElement()->InitBase(*url);
+          }
         }
         break;
       case kNameSpaceID_SVG:
diff --git a/parser/html/nsHtml5TreeOpExecutor.cpp b/parser/html/nsHtml5TreeOpExecutor.cpp
index 02b62e9dded..0ef3a076b36 100644
--- a/parser/html/nsHtml5TreeOpExecutor.cpp
+++ b/parser/html/nsHtml5TreeOpExecutor.cpp
@@ -830,7 +830,18 @@ nsHtml5TreeOpExecutor::InitializeDocWriteParserState(nsAHtml5TreeBuilderState* a
 already_AddRefed<nsIURI>
 nsHtml5TreeOpExecutor::ConvertIfNotPreloadedYet(const nsAString& aURL)
 {
-  nsIURI* base = mDocument->GetDocBaseURI();
+  // The URL of the document without <base>
+  nsIURI* documentURI = mDocument->GetDocumentURI();
+  // The URL of the document with non-speculative <base>
+  nsIURI* documentBaseURI = mDocument->GetDocBaseURI();
+
+  // If the two above are different, use documentBaseURI. If they are the
+  // same, the document object isn't aware of a <base>, so attempt to use the
+  // mSpeculationBaseURI or, failing, that, documentURI.
+  nsIURI* base = (documentURI == documentBaseURI) ?
+                  (mSpeculationBaseURI ?
+                   mSpeculationBaseURI.get() : documentURI)
+                 : documentBaseURI;
   const nsCString& charset = mDocument->GetDocumentCharacterSet();
   nsCOMPtr<nsIURI> uri;
   nsresult rv = NS_NewURI(getter_AddRefs(uri), aURL, charset.get(), base);
@@ -882,6 +893,21 @@ nsHtml5TreeOpExecutor::PreloadImage(const nsAString& aURL)
   mDocument->MaybePreLoadImage(uri);
 }
 
+void
+nsHtml5TreeOpExecutor::SetSpeculationBase(const nsAString& aURL)
+{
+  if (mSpeculationBaseURI) {
+    // the first one wins
+    return;
+  }
+  const nsCString& charset = mDocument->GetDocumentCharacterSet();
+  nsresult rv = NS_NewURI(getter_AddRefs(mSpeculationBaseURI), aURL,
+      charset.get(), mDocument->GetDocumentURI());
+  if (NS_FAILED(rv)) {
+    NS_WARNING("Failed to create a URI");
+  }
+}
+
 #ifdef DEBUG_NS_HTML5_TREE_OP_EXECUTOR_FLUSH
 PRUint32 nsHtml5TreeOpExecutor::sAppendBatchMaxSize = 0;
 PRUint32 nsHtml5TreeOpExecutor::sAppendBatchSlotsExamined = 0;
diff --git a/parser/html/nsHtml5TreeOpExecutor.h b/parser/html/nsHtml5TreeOpExecutor.h
index 5a44f4f4189..02814e32d2a 100644
--- a/parser/html/nsHtml5TreeOpExecutor.h
+++ b/parser/html/nsHtml5TreeOpExecutor.h
@@ -109,6 +109,8 @@ class nsHtml5TreeOpExecutor : public nsContentSink,
      */
     nsCStringHashSet mPreloadedURLs;
 
+    nsCOMPtr<nsIURI> mSpeculationBaseURI;
+
     /**
      * Whether the parser has started
      */
@@ -395,6 +397,8 @@ class nsHtml5TreeOpExecutor : public nsContentSink,
 
     void PreloadImage(const nsAString& aURL);
 
+    void SetSpeculationBase(const nsAString& aURL);
+
   private:
 
     nsHtml5Tokenizer* GetTokenizer();