diff --git a/CMakeLists.txt b/CMakeLists.txt
index 6cd051909d..e90744ba76 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1029,13 +1029,13 @@ else()
   set (ADDITIONAL_CUSTOM_CONTENT "\nif [ -e \"\${aScriptPath}/${SUB_CUSTOM_NAME}\" ]; then\n  source \"\${aScriptPath}/${SUB_CUSTOM_NAME}\" \"\$1\" \"\$2\" \nfi")
 endif()
 
- # change custom.bat/sh
-if (EXISTS "${INSTALL_DIR}/${INSTALL_DIR_SCRIPT}/custom.${SCRIPT_EXT}")
+# validating custom.bat/sh for changes
+if (EXISTS "${CMAKE_BINARY_DIR}/custom.${SCRIPT_EXT}" AND EXISTS "${INSTALL_DIR}/${INSTALL_DIR_SCRIPT}/custom.${SCRIPT_EXT}")
   file (READ "${INSTALL_DIR}/${INSTALL_DIR_SCRIPT}/custom.${SCRIPT_EXT}" CUSTOM_CONTENT)
-
-  set (CUSTOM_CONTENT "${CUSTOM_CONTENT} ${ADDITIONAL_CUSTOM_CONTENT}")
-
-  file (WRITE "${INSTALL_DIR}/${INSTALL_DIR_SCRIPT}/custom.${SCRIPT_EXT}" "${CUSTOM_CONTENT}")
+  if (NOT "${CUSTOM_CONTENT}" MATCHES "${ADDITIONAL_CUSTOM_CONTENT}")
+    set (CUSTOM_CONTENT "${CUSTOM_CONTENT} ${ADDITIONAL_CUSTOM_CONTENT}")
+    OCCT_CONFIGURE_AND_INSTALL ("adm/templates/custom.${SCRIPT_EXT}.main" "custom.${SCRIPT_EXT}" "custom.${SCRIPT_EXT}" "${CUSTOM_CONTENT}")
+  endif()
 else()
   OCCT_CONFIGURE_AND_INSTALL ("adm/templates/custom.${SCRIPT_EXT}.main" "custom.${SCRIPT_EXT}" "custom.${SCRIPT_EXT}" "${INSTALL_DIR_SCRIPT}")
 endif()