Index: apt-0.9.7.9~exp3+ll1/apt-pkg/acquire-worker.cc
===================================================================
--- apt-0.9.7.9~exp3+ll1.orig/apt-pkg/acquire-worker.cc	2013-04-17 18:04:29.337393497 -0700
+++ apt-0.9.7.9~exp3+ll1/apt-pkg/acquire-worker.cc	2013-04-22 15:55:41.402029216 -0700
@@ -305,7 +305,15 @@
 	    
 	    OwnerQ->ItemDone(Itm);
 	    unsigned long long const ServerSize = strtoull(LookupTag(Message,"Size","0").c_str(), NULL, 10);
-	    if (TotalSize != 0 && ServerSize != TotalSize)
+            bool isHit = StringToBool(LookupTag(Message,"IMS-Hit"),false) ||
+                         StringToBool(LookupTag(Message,"Alt-IMS-Hit"),false);
+            // Using the https method the server might return 200, but the
+            // If-Modified-Since condition is not satsified, libcurl will
+            // discard the download. In this case, however, TotalSize will be
+            // set to the actual size of the file, while ServerSize will be set
+            // to 0. Therefore, if the item is marked as a hit and the
+            // downloaded size (ServerSize) is 0, we ignore TotalSize.
+	    if (TotalSize != 0 && (!isHit || ServerSize != 0) && ServerSize != TotalSize)
 	       _error->Warning("Size of file %s is not what the server reported %s %llu",
 			       Owner->DestFile.c_str(), LookupTag(Message,"Size","0").c_str(),TotalSize);
 
@@ -332,8 +340,7 @@
 	    // Log that we are done
 	    if (Log != 0)
 	    {
-	       if (StringToBool(LookupTag(Message,"IMS-Hit"),false) == true ||
-		   StringToBool(LookupTag(Message,"Alt-IMS-Hit"),false) == true)
+	       if (isHit)
 	       {
 		  /* Hide 'hits' for local only sources - we also manage to
 		     hide gets */
Index: apt-0.9.7.9~exp3+ll1/debian/control
===================================================================
--- apt-0.9.7.9~exp3+ll1.orig/debian/control	2013-04-17 18:03:17.970155119 -0700
+++ apt-0.9.7.9~exp3+ll1/debian/control	2013-04-17 18:04:00.941696327 -0700
@@ -7,7 +7,7 @@
  Julian Andres Klode <jak@debian.org>
 Standards-Version: 3.9.3
 Build-Depends: dpkg-dev (>= 1.15.8), debhelper (>= 8.1.3~), libdb-dev,
- gettext (>= 0.12), libcurl4-gnutls-dev (>= 7.19.0),
+ gettext (>= 0.12), libcurl4-gnutls-dev (>= 7.19.4~),
  zlib1g-dev, libbz2-dev, xsltproc, docbook-xsl, docbook-xml,
  po4a (>= 0.34-2), autotools-dev, autoconf, automake
 Build-Depends-Indep: doxygen, debiandoc-sgml
Index: apt-0.9.7.9~exp3+ll1/methods/https.cc
===================================================================
--- apt-0.9.7.9~exp3+ll1.orig/methods/https.cc	2013-04-17 18:03:17.978155034 -0700
+++ apt-0.9.7.9~exp3+ll1/methods/https.cc	2013-04-17 18:04:46.457211070 -0700
@@ -285,6 +285,11 @@
    long curl_servdate;
    curl_easy_getinfo(curl, CURLINFO_FILETIME, &curl_servdate);
 
+   // If the server returns 200 OK but the If-Modified-Since condition is not
+   // met, CURLINFO_CONDITION_UNMET will be set to 1
+   long curl_condition_unmet = 0;
+   curl_easy_getinfo(curl, CURLINFO_CONDITION_UNMET, &curl_condition_unmet);
+
    File->Close();
 
    // cleanup
@@ -312,7 +317,7 @@
       Res.Filename = File->Name();
       Res.LastModified = Buf.st_mtime;
       Res.IMSHit = false;
-      if (curl_responsecode == 304)
+      if (curl_responsecode == 304 || curl_condition_unmet)
       {
 	 unlink(File->Name().c_str());
 	 Res.IMSHit = true;