diff --git a/pkgs/development/compilers/gavrasm/default.nix b/pkgs/development/compilers/gavrasm/default.nix
index 6bd813b56cf..0a969a80c12 100644
--- a/pkgs/development/compilers/gavrasm/default.nix
+++ b/pkgs/development/compilers/gavrasm/default.nix
@@ -1,36 +1,45 @@
 { lib, stdenv, fetchzip, fpc , lang ? "en" } :
+
 assert lib.assertOneOf "lang" lang ["cn" "de" "en" "fr" "tr"];
+
 stdenv.mkDerivation rec {
   pname = "gavrasm";
-  version = "4.5";
+  version = "5.1";
+  flatVersion = lib.strings.replaceStrings ["."] [""] version;
 
   src = fetchzip {
-    url ="http://www.avr-asm-tutorial.net/gavrasm/v45/gavrasm_sources_lin_45.zip";
-    sha256 = "1f5g5ran74pznwj4g7vfqh2qhymaj3p26f2lvzbmlwq447iid52c";
+    url = "http://www.avr-asm-tutorial.net/gavrasm/v${flatVersion}/gavrasm_sources_lin_${flatVersion}.zip";
+    sha256 = "0k94f8k4980wvhx3dpl1savpx4wqv9r5090l0skg2k8vlhsv58gf";
     stripRoot=false;
   };
 
   nativeBuildInputs = [ fpc ];
 
   configurePhase = ''
+    runHook preConfigure
     cp gavrlang_${lang}.pas gavrlang.pas
+    runHook postConfigure
   '';
 
   buildPhase = ''
+    runHook preBuild
     fpc gavrasm.pas
+    runHook postBuild
   '';
 
   installPhase = ''
+    runHook preInstall
     mkdir -p $out/bin
     cp gavrasm $out/bin
     mkdir -p $out/doc
     cp instr.asm $out/doc
     cp ReadMe.Txt $out/doc
     cp LiesMich.Txt $out/doc
+    runHook postInstall
   '';
 
   meta = with lib; {
-    homepage = "http://www.avr-asm-tutorial.net/gavrasm";
+    homepage = "http://www.avr-asm-tutorial.net/gavrasm/";
     description = "AVR Assembler for ATMEL AVR-Processors";
     license = licenses.unfree;
     maintainers = with maintainers; [ mafo ];