diff --git a/pkgs/by-name/jw/jwasm/package.nix b/pkgs/by-name/jw/jwasm/package.nix
index 8a1390aac9f5c..a1cf1a9cf5c0b 100644
--- a/pkgs/by-name/jw/jwasm/package.nix
+++ b/pkgs/by-name/jw/jwasm/package.nix
@@ -25,6 +25,10 @@ stdenv.mkDerivation (finalAttrs: {
       --replace "/usr/local/bin" "${placeholder "out"}/bin"
   '';
 
+  preInstall = ''
+    mkdir -p ${placeholder "out"}/bin
+  '';
+
   postInstall = ''
     install -Dpm644 $src/Html/License.html \
                     $src/Html/Manual.html \
@@ -36,6 +40,7 @@ stdenv.mkDerivation (finalAttrs: {
     homepage = "https://github.com/Baron-von-Riedesel/JWasm/";
     description = "MASM-compatible x86 assembler";
     changelog = "https://github.com/Baron-von-Riedesel/JWasm/releases/tag/${finalAttrs.src.rev}";
+    mainProgram = "jwasm";
     license = lib.licenses.gpl2Plus;
     maintainers = with lib.maintainers; [ AndersonTorres ];
     platforms = lib.platforms.unix;