diff --git a/flake.nix b/flake.nix
index 325e892..d0a953e 100644
--- a/flake.nix
+++ b/flake.nix
@@ -70,9 +70,8 @@
 
         buildPhase = ''
           make \
-            MRBC=${mruby}/bin/mrbc \
-            MRUBY_CFLAGS=-I${mruby}/include \
-            MRUBY_LIBS=-L${mruby}/lib -lmruby
+            MRUBY_CFLAGS="-I${mruby}/include" \
+            MRUBY_LIBS="-L${mruby}/lib -lmruby"
         '';
 
         installPhase = ''
@@ -110,7 +109,6 @@
           export CC="ccache $CC"
           export CXX="ccache $CXX"
 
-          export MRBC=${mruby}/bin/mrbc
           export MRUBY_CFLAGS=-I${mruby}/include
           export MRUBY_LIBS="-L${mruby}/lib -lmruby"
           export PATH="$PWD/result/bin:$PATH"