diff --git a/CMakeLists.txt b/CMakeLists.txt
index d86ae96cc..e979d4f38 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -543,10 +543,7 @@ if(NOT CMake_TEST_EXTERNAL_CMAKE)
         "${CMake_VERSION_MAJOR}.${CMake_VERSION_MINOR}.${CMake_VERSION_PATCH}")
       set(CMAKE_BUNDLE_LOCATION "${CMAKE_INSTALL_PREFIX}")
       # make sure CMAKE_INSTALL_PREFIX ends in /
-      string(LENGTH "${CMAKE_INSTALL_PREFIX}" LEN)
-      math(EXPR LEN "${LEN} -1" )
-      string(SUBSTRING "${CMAKE_INSTALL_PREFIX}" ${LEN} 1 ENDCH)
-      if(NOT "${ENDCH}" STREQUAL "/")
+      if(NOT CMAKE_INSTALL_PREFIX MATCHES "/$")
         set(CMAKE_INSTALL_PREFIX "${CMAKE_INSTALL_PREFIX}/")
       endif()
       set(CMAKE_INSTALL_PREFIX