diff --git a/pkgs/build-support/vm/default.nix b/pkgs/build-support/vm/default.nix
index 4c97da91fd1f..008a41f082f2 100644
--- a/pkgs/build-support/vm/default.nix
+++ b/pkgs/build-support/vm/default.nix
@@ -290,7 +290,7 @@ rec {
     args = ["-e" (vmRunCommand qemuCommandLinux)];
     origArgs = attrs.args;
     origBuilder = attrs.builder;
-    QEMU_OPTS = "-m ${toString (attrs.memSize or 512)}";
+    QEMU_OPTS = "${attrs.QEMU_OPTS or ""} -m ${toString (attrs.memSize or 512)}";
   });
 
 
@@ -1024,26 +1024,26 @@ rec {
       packages = commonOpenSUSEPackages;
     };
 
-    centos64i386 = {
-      name = "centos-6.4-i386";
-      fullName = "CentOS 6.4 (i386)";
+    centos65i386 = {
+      name = "centos-6.5-i386";
+      fullName = "CentOS 6.5 (i386)";
       packagesList = fetchurl {
-        url = http://mirror.centos.org/centos/6.4/os/i386/repodata/87aa4c4e19f9a3ec93e3d820f1ea6b6ece8810cb45f117a16354465e57a1b50d-primary.xml.gz;
-        sha256 = "03dml5bmwijlcfhigwa5rc88ikkfdgmg286qwf9yr8zr3574ral7";
+        url = http://mirror.centos.org/centos/6.5/os/i386/repodata/a89f27cc7d3cea431f3bd605a1e9309c32d5d409abc1b51a7b5c71c05f18a0c2-primary.xml.gz;
+        sha256 = "1hm031gw0wawgcdbbhdb17adaclw63ls21fn7cgl7siwgp62g7x8";
       };
-      urlPrefix = http://mirror.centos.org/centos/6.4/os/i386/ ;
+      urlPrefix = http://mirror.centos.org/centos/6.5/os/i386/ ;
       archs = ["noarch" "i386"];
       packages = commonCentOSPackages;
     };
 
-    centos64x86_64 = {
-      name = "centos-6.4-x86_64";
-      fullName = "CentOS 6.4 (x86_64)";
+    centos65x86_64 = {
+      name = "centos-6.5-x86_64";
+      fullName = "CentOS 6.5 (x86_64)";
       packagesList = fetchurl {
-        url = http://mirror.centos.org/centos/6.4/os/x86_64/repodata/4d4030b92f010f466eb4f004312b9f532b9e85e60c5e6421e8b429c180ac1efe-primary.xml.gz;
-        sha256 = "1zhymj0c2adlx0hn8phcws2rwaskkwmk217hnip4c3q15ywk0h2d";
+        url = http://mirror.centos.org/centos/6.5/os/x86_64/repodata/3353e378f5cb4bb6c3b3dd2ca266c6d68a1e29c36cf99f76aea3d8e158626024-primary.xml.gz;
+        sha256 = "0930c9cf3n53mrv9zybcqclix2nnqrka4b6xng1vcjybymwf6lrk";
       };
-      urlPrefix = http://mirror.centos.org/centos/6.4/os/x86_64/ ;
+      urlPrefix = http://mirror.centos.org/centos/6.5/os/x86_64/ ;
       archs = ["noarch" "x86_64"];
       packages = commonCentOSPackages;
     };