diff --git a/cmake/FindROOT.cmake b/cmake/FindROOT.cmake
index 6855cb6f2..69c0a9bf3 100644
--- a/cmake/FindROOT.cmake
+++ b/cmake/FindROOT.cmake
@@ -1,25 +1,27 @@
 # - Finds ROOT instalation
-# This module sets up ROOT information 
+# This module sets up ROOT information
 # It defines:
 # ROOT_FOUND          If the ROOT is found
 # ROOT_INCLUDE_DIR    PATH to the include directory (deprecated)
 # ROOT_INCLUDE_DIRS   PATH to the include directory
 # ROOT_LIBRARIES      Most common libraries
-# ROOT_LIBRARY_DIR    PATH to the library directory 
+# ROOT_LIBRARY_DIR    PATH to the library directory
 # ROOT_BIN_DIR	      PATH to the excutables directory
 # ROOT_PYTHONVER      Compatible python version string
 
-# First search for ROOTConfig.cmake on the path defined via user setting 
+# First search for ROOTConfig.cmake on the path defined via user setting
 # ROOT_DIR
 
 if (CMAKE_SYSTEM_NAME MATCHES "Windows")
 
   if(DEFINED ENV{ROOTSYS})
-   set(ROOTSYS $ENV{ROOTSYS})
+    set(ROOTSYS $ENV{ROOTSYS})
+  else()
+    message(FATAL_ERROR "ROOTSYS environment variable is undefined. Did you forget to source the `thisroot.bat`?")
   endif()
 
   if(NOT ROOTSYS)
-	set(ROOT_FOUND FALSE)
+    set(ROOT_FOUND FALSE)
   else()
     set(ROOT_FOUND TRUE)
 
@@ -27,17 +29,17 @@ if (CMAKE_SYSTEM_NAME MATCHES "Windows")
     set(ROOT_INCLUDE_DIRS ${ROOTSYS}/include)
     set(ROOT_BIN_DIR ${ROOTSYS}/bin)
     set(ROOTCINT_EXECUTABLE ${ROOTSYS}/bin/rootcint.exe)
-	set(GENREFLEX_EXECUTABLE ${ROOTSYS}/bin/genreflex.exe)
+    set(GENREFLEX_EXECUTABLE ${ROOTSYS}/bin/genreflex.exe)
 
     set(CMAKE_FIND_LIBRARY_PREFIXES "lib")
     set(CMAKE_FIND_LIBRARY_SUFFIXES ".lib" ".dll")
     set(ROOT_LIBRARIES)
     foreach(_cpt Core Imt RIO Net Hist Gui Eve RGL Gdml Geom Graf Graf3d Gpad Tree TreePlayer Rint Postscript Matrix Physics MathCore Thread MultiProc Minuit)
       find_library(ROOT_${_cpt}_LIBRARY ${_cpt} HINTS ${ROOT_LIBRARY_DIR})
-        if(ROOT_${_cpt}_LIBRARY)
-          mark_as_advanced(ROOT_${_cpt}_LIBRARY)
-		    list(APPEND ROOT_LIBRARIES ${ROOT_${_cpt}_LIBRARY})
-		  endif()
+      if(ROOT_${_cpt}_LIBRARY)
+        mark_as_advanced(ROOT_${_cpt}_LIBRARY)
+	list(APPEND ROOT_LIBRARIES ${ROOT_${_cpt}_LIBRARY})
+      endif()
     endforeach()
     if(ROOT_LIBRARIES)
       list(REMOVE_DUPLICATES ROOT_LIBRARIES)
@@ -51,26 +53,21 @@ else()
 
   if(NOT ROOT_CONFIG_EXECUTABLE)
     set(ROOT_FOUND FALSE)
-  else()    
+  else()
     set(ROOT_FOUND TRUE)
 
-
-	execute_process(
-      COMMAND ${ROOT_CONFIG_EXECUTABLE} --incdir 
+    execute_process(
+      COMMAND ${ROOT_CONFIG_EXECUTABLE} --incdir
       OUTPUT_VARIABLE ROOT_INCLUDE_DIRS
       OUTPUT_STRIP_TRAILING_WHITESPACE)
 
-	execute_process(
-      COMMAND ${ROOT_CONFIG_EXECUTABLE} --libdir 
+    execute_process(
+      COMMAND ${ROOT_CONFIG_EXECUTABLE} --libdir
       OUTPUT_VARIABLE ROOT_LIBRARY_DIR
       OUTPUT_STRIP_TRAILING_WHITESPACE)
 
-
-    set(ROOTCINT_EXECUTABLE $ENV{ROOTSYS}/bin/rootcint)
-	set(GENREFLEX_EXECUTABLE $ENV{ROOTSYS}/bin/genreflex)
-
     execute_process(
-      COMMAND ${ROOT_CONFIG_EXECUTABLE} --version 
+      COMMAND ${ROOT_CONFIG_EXECUTABLE} --version
       OUTPUT_VARIABLE ROOT_VERSION
       OUTPUT_STRIP_TRAILING_WHITESPACE)
 
@@ -84,15 +81,18 @@ else()
       OUTPUT_VARIABLE ROOT_BIN_DIR
       OUTPUT_STRIP_TRAILING_WHITESPACE)
 
-	# Make variables changeble to the advanced user
+    set(ROOTCINT_EXECUTABLE ${ROOT_BIN_DIR}/rootcint)
+    set(GENREFLEX_EXECUTABLE ${ROOT_BIN_DIR}/genreflex)
+
+    # Make variables changeble to the advanced user
     mark_as_advanced(ROOT_CONFIG_EXECUTABLE)
   endif()
 endif()
 
 
 if (NOT ROOT_FOUND)
-    message(FATAL_ERROR "ROOT required, but not found")
+  message(FATAL_ERROR "ROOT required, but not found")
 else()
-	message(STATUS "Find ROOT ${ROOT_VERSION} in ${ROOT_BIN_DIR}")
+  message(STATUS "Find ROOT ${ROOT_VERSION} in ${ROOT_BIN_DIR}")
 endif()