diff --git a/autoload/codepainter.vim b/autoload/codepainter.vim
index 92ed606..e0ff5fa 100644
--- a/autoload/codepainter.vim
+++ b/autoload/codepainter.vim
@@ -21,6 +21,7 @@ let g:marks = {}
 let g:vim_index = 0
 let g:navigation_index = 0
 let g:has_nvim = has('nvim')
+let g:codepainter_file_keep_original_extension = 1
 
 "dictionary holding the markings folowing this structure
 "marks = {
@@ -216,11 +217,31 @@ endfunc
 
 func! codepainter#SaveMarks(...) abort
     let l:path = a:0 == 0 ? expand("%") : substitute(a:1, "\"", "","g")
-    let l:aux = expand("%:e")
+    let l:aux = fnamemodify(expand(l:path), ':e')
     if len(l:aux) == 0
+        " If no extension add .json
         let l:path = l:path . ".json"
     else
-        let l:path = substitute(l:path, expand("%:e"), "json", "")
+        if l:aux ==# 'json'
+            " Path already ends with .json
+            " Potential overwrite if script with marks is also a JSON
+            " Opt. A: echo error and return
+            if a:0 == 0
+                echom "Current script is JSON"
+                echom "Pass an arg to PainterSaveMarks to store the codepainters"
+                return
+            endif
+            " Opt. B: replace all next '.json' with '_codepainter.json'
+            " (not coded)
+        else
+            if g:codepainter_file_keep_original_extension
+                " Add .json to path keeping original extension
+                let l:path = expand('%:p') . '.json'
+            else
+                " Replace extension with .json
+                let l:path = expand('%:p:r') . '.json'
+            endif
+        endif
     endif
     let jsonString = json_encode(g:marks)
     execute ("redir! >" . l:path)
@@ -232,11 +253,18 @@ endfunc
 func! codepainter#LoadMarks(...) abort
     let l:path = a:0 == 0 ? expand("%") : substitute(a:1, "\"", "","g")
     if a:0 == 0
-        let l:aux = expand("%:e")
+        let l:aux = fnamemodify(expand(l:path), ':e')
         if len(l:aux) == 0
+            " If no extension add .json
             let l:path = l:path . ".json"
         else
-            let l:path = substitute(l:path, expand("%:e"), "json", "")
+            if g:codepainter_file_keep_original_extension
+                " Add .json to path keeping original extension
+                let l:path = expand('%:p') . '.json'
+            else
+                " Replace extension with .json
+                let l:path = expand('%:p:r') . '.json'
+            endif
         endif
     endif
     let l:file = readfile(l:path)
diff --git a/plugin/codepainter.vim b/plugin/codepainter.vim
index a57cd53..7ca7bd0 100644
--- a/plugin/codepainter.vim
+++ b/plugin/codepainter.vim
@@ -15,5 +15,5 @@ command! -nargs=1 PainterPickColor          silent! call codepainter#ChangeColor
 command! -nargs=1 PainterPickColorByName    silent! call codepainter#ChangeColorByName(<f-args>)
 command! -nargs=0 PainterEraseAll           silent! call codepainter#EraseAll()
 command! -nargs=? PainterEraseLine          silent! call codepainter#EraseLine(<f-args>)
-command! -nargs=? PainterSaveMarks          silent! call codepainter#SaveMarks(<f-args>)
+command! -nargs=? PainterSaveMarks          call codepainter#SaveMarks(<f-args>)
 command! -nargs=? PainterLoadMarks          silent! call codepainter#LoadMarks(<f-args>)