diff --git a/pkgs/development/compilers/yasm/default.nix b/pkgs/development/compilers/yasm/default.nix
new file mode 100644
index 000000000000..c0da59515174
--- /dev/null
+++ b/pkgs/development/compilers/yasm/default.nix
@@ -0,0 +1,16 @@
+{stdenv, fetchurl}:
+
+stdenv.mkDerivation rec {
+  name = "yasm-2.05.01";
+  
+  src = fetchurl {
+    url = http://www.tortall.net/projects/yasm/releases/yasm-1.0.0.tar.gz;
+    sha256 = "0nd95r9y5r3p9mvdyj1yhvlz9zjw0id1g470c7i1p3p0x0n6zc06";
+  };
+
+  meta = {
+    homepage = http://www.tortall.net/projects/yasm/;
+    description = "Complete rewrite of the NASM assembler";
+    license = "BSD";
+  };
+}
diff --git a/pkgs/development/libraries/x264/default.nix b/pkgs/development/libraries/x264/default.nix
index e6fbb6d5cc58..6928f9f6df4b 100644
--- a/pkgs/development/libraries/x264/default.nix
+++ b/pkgs/development/libraries/x264/default.nix
@@ -1,4 +1,4 @@
-{ stdenv, fetchurl }:
+{stdenv, fetchurl, yasm}:
 
 stdenv.mkDerivation rec {
   version = "snapshot-20100429-2245";
@@ -13,7 +13,9 @@ stdenv.mkDerivation rec {
     sed -i s,/bin/bash,${stdenv.shell}, configure version.sh
   '';
 
-  configureFlags = [ "--disable-asm" "--enable-shared" ];
+  configureFlags = [ "--enable-shared" ];
+
+  buildInputs = [ yasm ];
 
   meta = { 
       description = "library for encoding H264/AVC video streams";
diff --git a/pkgs/development/libraries/xvidcore/default.nix b/pkgs/development/libraries/xvidcore/default.nix
index b02ae2b14e9b..7276402cbf5d 100644
--- a/pkgs/development/libraries/xvidcore/default.nix
+++ b/pkgs/development/libraries/xvidcore/default.nix
@@ -1,4 +1,4 @@
-{stdenv, fetchurl}:
+{stdenv, fetchurl, nasm}:
 
 stdenv.mkDerivation rec {
   name = "xvidcore-1.2.2";
@@ -11,6 +11,8 @@ stdenv.mkDerivation rec {
   preConfigure = ''
     cd build/generic
   '';
+
+  buildInputs = [ nasm ];
   
   meta = {
     description = "MPEG-4 video codec for PC";
diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index fa0f47f370c1..1b16caf967ef 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -2604,6 +2604,9 @@ let
     inherit fetchurl stdenv;
   };
 
+  yasm = import ../development/compilers/yasm {
+    inherit fetchurl stdenv;
+  };
 
   ### DEVELOPMENT / INTERPRETERS
 
@@ -5202,7 +5205,7 @@ let
     };
 
   x264 = import ../development/libraries/x264 {
-    inherit fetchurl stdenv;
+    inherit fetchurl stdenv yasm;
   };
 
   xapian = makeOverridable (import ../development/libraries/xapian) {
@@ -5248,7 +5251,7 @@ let
   };
 
   xvidcore = import ../development/libraries/xvidcore {
-    inherit fetchurl stdenv;
+    inherit fetchurl stdenv nasm;
   };
 
   zangband = builderDefsPackage (import ../games/zangband) {