diff --git a/nemu/default.nix b/nemu/default.nix
index 53765d6..a886b79 100644
--- a/nemu/default.nix
+++ b/nemu/default.nix
@@ -27,8 +27,6 @@ stdenv.mkDerivation rec {
     am-kernels
   ];
 
-  IMAGES_PATH = "${am-kernels}/share/images";
-
   configurePhase = ''
     export NEMU_HOME=$(pwd)
     make alldefconfig
@@ -40,6 +38,7 @@ stdenv.mkDerivation rec {
 
   doCheck = true;
   checkPhase = ''
+    export IMAGES_PATH=${am-kernels}/share/images
     make test
   '';
 
@@ -48,6 +47,11 @@ stdenv.mkDerivation rec {
     make PREFIX=$out install
   '';
 
+  shellHook = ''
+    export NEMU_HOME=$(pwd)
+    export IMAGES_PATH=${am-kernels}/share/images
+  '';
+
   meta = with lib; {
     description = "NJU EMUlator, a full system x86/mips32/riscv32/riscv64 emulator for teaching";
     homepage = "https://github.com/NJU-ProjectN/nemu.git";