diff --git a/reactos/install.bat b/reactos/install.bat
index d16ff5a5ccb..405cef1ce71 100644
--- a/reactos/install.bat
+++ b/reactos/install.bat
@@ -3,6 +3,9 @@ if "%1" == "" goto NoParameter
 set ROS_INSTALL=%1
 goto Install
 :NoParameter
+if "%ROS_INSTALL%" == "" goto UseDefault
+goto Install
+:UseDefault
 set ROS_INSTALL=c:\reactos
 :Install
 echo Installing to %ROS_INSTALL%
diff --git a/reactos/rules.mak b/reactos/rules.mak
index b0eca943f89..a15386964de 100644
--- a/reactos/rules.mak
+++ b/reactos/rules.mak
@@ -57,10 +57,12 @@ PIPE := -pipe
 endif
 
 
-# Set INSTALL_DIR to default value if not already set
-# ifeq ($(INSTALL_DIR),)
+# Use environment var ROS_INSTALL to override default install dir
+ifeq ($(ROS_INSTALL),)
 INSTALL_DIR = $(PATH_TO_TOP)/reactos
-# endif
+else
+INSTALL_DIR = $(ROS_INSTALL)
+endif
 
 # Set DIST_DIR to default value if not already set
 # ifeq ($(DIST_DIR),)