diff --git a/netwerk/protocol/http/src/nsHttpChannel.cpp b/netwerk/protocol/http/src/nsHttpChannel.cpp
index 03563b9da69d..22b494ab962f 100644
--- a/netwerk/protocol/http/src/nsHttpChannel.cpp
+++ b/netwerk/protocol/http/src/nsHttpChannel.cpp
@@ -449,12 +449,10 @@ nsHttpChannel::ProcessNotModified()
     rv = mCachedResponseHead->UpdateHeaders(mResponseHead->Headers());
     if (NS_FAILED(rv)) return rv;
 
-    // update the cached response headers
-    nsCAutoString headers;
-    rv = mCachedResponseHead->Flatten(headers, PR_TRUE);
-    if (NS_FAILED(rv)) return rv;
-
-    rv = mCacheEntry->SetMetaDataElement("http-headers", headers.get());
+    // update the cached response head
+    nsCAutoString head;
+    mCachedResponseHead->Flatten(head, PR_TRUE);
+    rv = mCacheEntry->SetMetaDataElement("response-head", head.get());
     if (NS_FAILED(rv)) return rv;
 
     // make the cached response be the current response
@@ -632,13 +630,24 @@ nsHttpChannel::CheckCache()
     if (!mCacheEntry || !(mCacheAccess & nsICache::ACCESS_READ))
         return NS_OK;
 
-    // Get the cached HTTP response headers
     nsXPIDLCString buf;
-    rv = mCacheEntry->GetMetaDataElement("http-headers", getter_Copies(buf));
-    if (NS_FAILED(rv)) {
-        NS_WARNING("cache entry does not contain http headers!");
-        return rv;
+
+    // Get the method that was used to generate the cached response
+    rv = mCacheEntry->GetMetaDataElement("request-method", getter_Copies(buf));
+    if (NS_FAILED(rv)) return rv;
+
+    nsHttpAtom method = nsHttp::ResolveAtom(buf);
+    if (method == nsHttp::Head) {
+        // The cached response does not contain an entity.  We can only reuse
+        // the response if the current request is also HEAD.
+        if (mRequestHead.Method() != nsHttp::Head)
+            return NS_OK;
     }
+    buf = 0;
+
+    // Get the cached HTTP response headers
+    rv = mCacheEntry->GetMetaDataElement("response-head", getter_Copies(buf));
+    if (NS_FAILED(rv)) return rv;
 
     // Parse the cached HTTP response headers
     NS_ASSERTION(!mCachedResponseHead, "memory leak detected");
@@ -647,8 +656,6 @@ nsHttpChannel::CheckCache()
         return NS_ERROR_OUT_OF_MEMORY;
     rv = mCachedResponseHead->Parse((char *) buf.get());
     if (NS_FAILED(rv)) return rv;
-
-    // we're done with the header buf
     buf = 0;
 
     // If we were only granted read access, then assume the entry is valid.
@@ -920,14 +927,16 @@ nsHttpChannel::CacheReceivedResponse()
     rv = UpdateExpirationTime();
     if (NS_FAILED(rv)) return rv;
 
-    // Store the received HTTP headers with the cache entry as an element of
-    // the meta data.
-
-    nsCAutoString headers;
-    rv = mResponseHead->Flatten(headers, PR_TRUE);
+    // Store the HTTP request method with the cache entry so we can distinguish
+    // for example GET and HEAD responses.
+    rv = mCacheEntry->SetMetaDataElement("request-method", mRequestHead.Method().get());
     if (NS_FAILED(rv)) return rv;
 
-    rv = mCacheEntry->SetMetaDataElement("http-headers", headers.get());
+    // Store the received HTTP head with the cache entry as an element of
+    // the meta data.
+    nsCAutoString head;
+    mResponseHead->Flatten(head, PR_TRUE);
+    rv = mCacheEntry->SetMetaDataElement("response-head", head.get());
     if (NS_FAILED(rv)) return rv;
 
     // Open an output stream to the cache entry and insert a listener tee into
diff --git a/netwerk/protocol/http/src/nsHttpHeaderArray.cpp b/netwerk/protocol/http/src/nsHttpHeaderArray.cpp
index 89eb064b526e..fb9f18152677 100644
--- a/netwerk/protocol/http/src/nsHttpHeaderArray.cpp
+++ b/netwerk/protocol/http/src/nsHttpHeaderArray.cpp
@@ -102,7 +102,7 @@ nsHttpHeaderArray::VisitHeaders(nsIHttpHeaderVisitor *visitor)
     return NS_OK;
 }
 
-nsresult
+void
 nsHttpHeaderArray::Flatten(nsACString &buf)
 {
     PRInt32 i, count = mHeaders.Count();
@@ -113,7 +113,6 @@ nsHttpHeaderArray::Flatten(nsACString &buf)
         buf.Append(entry->value);
         buf.Append("\r\n");
     }
-    return NS_OK;
 }
 
 const char *
diff --git a/netwerk/protocol/http/src/nsHttpHeaderArray.h b/netwerk/protocol/http/src/nsHttpHeaderArray.h
index 03df11c1b5a7..8502e340c7dc 100644
--- a/netwerk/protocol/http/src/nsHttpHeaderArray.h
+++ b/netwerk/protocol/http/src/nsHttpHeaderArray.h
@@ -43,7 +43,7 @@ public:
 
     nsresult VisitHeaders(nsIHttpHeaderVisitor *visitor);
 
-    nsresult Flatten(nsACString &);
+    void     Flatten(nsACString &);
 
     PRUint32 Count() { return (PRUint32) mHeaders.Count(); }
 
diff --git a/netwerk/protocol/http/src/nsHttpRequestHead.cpp b/netwerk/protocol/http/src/nsHttpRequestHead.cpp
index 0fbbf1d373e9..b9dbbb0b1466 100644
--- a/netwerk/protocol/http/src/nsHttpRequestHead.cpp
+++ b/netwerk/protocol/http/src/nsHttpRequestHead.cpp
@@ -27,7 +27,7 @@
 // nsHttpRequestHead
 //-----------------------------------------------------------------------------
 
-nsresult
+void
 nsHttpRequestHead::Flatten(nsACString &buf)
 {
     // note: the first append is intentional.
@@ -51,7 +51,4 @@ nsHttpRequestHead::Flatten(nsACString &buf)
     buf.Append("\r\n");
 
     mHeaders.Flatten(buf);
-
-    // do not append the final \r\n
-    return NS_OK;
 }
diff --git a/netwerk/protocol/http/src/nsHttpRequestHead.h b/netwerk/protocol/http/src/nsHttpRequestHead.h
index c7f62f48a3d2..dc7479d8c169 100644
--- a/netwerk/protocol/http/src/nsHttpRequestHead.h
+++ b/netwerk/protocol/http/src/nsHttpRequestHead.h
@@ -51,9 +51,9 @@ public:
     const char *PeekHeader(nsHttpAtom h)            { return mHeaders.PeekHeader(h); }
     nsresult SetHeader(nsHttpAtom h, const char *v) { return mHeaders.SetHeader(h, v); }
     nsresult GetHeader(nsHttpAtom h, char **v)      { return mHeaders.GetHeader(h, v); }
-    void     ClearHeaders()                         { mHeaders.Clear(); }
+    void ClearHeaders()                             { mHeaders.Clear(); }
 
-    nsresult Flatten(nsACString &);
+    void Flatten(nsACString &);
 
 private:
     nsHttpHeaderArray mHeaders;
diff --git a/netwerk/protocol/http/src/nsHttpResponseHead.cpp b/netwerk/protocol/http/src/nsHttpResponseHead.cpp
index d95d2ce7d70a..12715709563d 100644
--- a/netwerk/protocol/http/src/nsHttpResponseHead.cpp
+++ b/netwerk/protocol/http/src/nsHttpResponseHead.cpp
@@ -30,11 +30,11 @@
 // nsHttpResponseHead <public>
 //-----------------------------------------------------------------------------
 
-nsresult
+void
 nsHttpResponseHead::Flatten(nsACString &buf, PRBool pruneTransients)
 {
     if (mVersion == NS_HTTP_VERSION_0_9)
-        return NS_OK;
+        return;
 
     buf.Append("HTTP/");
     if (mVersion == NS_HTTP_VERSION_1_1)
@@ -50,8 +50,10 @@ nsHttpResponseHead::Flatten(nsACString &buf, PRBool pruneTransients)
     buf.Append(mStatusText);
     buf.Append("\r\n");
 
-    if (!pruneTransients)
-        return mHeaders.Flatten(buf);
+    if (!pruneTransients) {
+        mHeaders.Flatten(buf);
+        return;
+    }
 
     // otherwise, we need to iterate over the headers and only flatten
     // those that are appropriate.
@@ -79,7 +81,6 @@ nsHttpResponseHead::Flatten(nsACString &buf, PRBool pruneTransients)
         buf.Append(value);
         buf.Append("\r\n");
     }
-    return NS_OK;
 }
 
 nsresult
diff --git a/netwerk/protocol/http/src/nsHttpResponseHead.h b/netwerk/protocol/http/src/nsHttpResponseHead.h
index 7bc3759cbcab..9dd982b11be6 100644
--- a/netwerk/protocol/http/src/nsHttpResponseHead.h
+++ b/netwerk/protocol/http/src/nsHttpResponseHead.h
@@ -59,7 +59,7 @@ public:
     // write out the response status line and headers as a single text block,
     // optionally pruning out transient headers (ie. headers that only make
     // sense the first time the response is handled).
-    nsresult Flatten(nsACString &, PRBool pruneTransients);
+    void     Flatten(nsACString &, PRBool pruneTransients);
 
     // parse flattened response head. block must be null terminated. parsing is
     // destructive.
diff --git a/netwerk/protocol/http/src/nsHttpTransaction.cpp b/netwerk/protocol/http/src/nsHttpTransaction.cpp
index 94bbc3920ad8..62c0cb812c75 100644
--- a/netwerk/protocol/http/src/nsHttpTransaction.cpp
+++ b/netwerk/protocol/http/src/nsHttpTransaction.cpp
@@ -84,9 +84,7 @@ nsHttpTransaction::SetupRequest(nsHttpRequestHead *requestHead,
         mNoContent = PR_TRUE;
 
     mReqHeaderBuf.SetLength(0);
-
-    rv = requestHead->Flatten(mReqHeaderBuf);
-    if (NS_FAILED(rv)) return rv;
+    requestHead->Flatten(mReqHeaderBuf);
 
     LOG2(("http request [\n%s]\n", mReqHeaderBuf.get()));