diff --git a/toolchain/emul b/toolchain/emul
index d468481..d7ef0f2 100755
--- a/toolchain/emul
+++ b/toolchain/emul
@@ -9,10 +9,8 @@ if [ -z ${MITTOS64+x} ]; then
   exit 1
 fi
 
-sysroot=/opt/sysroot
 iso=/opt/mittos64.iso
 
-mkdir -p ${sysroot}
+/opt/toolchain/mkiso
 
-grub-mkrescue -o ${iso} ${sysroot}
 qemu-system-x86_64 -cdrom ${iso} -curses
diff --git a/toolchain/mkiso b/toolchain/mkiso
new file mode 100755
index 0000000..c57a045
--- /dev/null
+++ b/toolchain/mkiso
@@ -0,0 +1,17 @@
+#!/bin/sh -e
+
+if [ -z ${MITTOS64+x} ]; then
+  echo -en "\033[31mWarning: \033[0m"
+  echo "It seems you are trying to build mittos64 in an unsuported environment."
+  echo "This makefile is designed to run inside a mittos64-specific docker container."
+  echo "If you know what you're doing, define the environment variable "MITTOS64""
+  echo "See README.md for more information"
+  exit 1
+fi
+
+sysroot=/opt/sysroot
+iso=/opt/mittos64.iso
+
+mkdir -p ${sysroot}
+
+grub-mkrescue -o ${iso} ${sysroot}