diff --git a/autoload/ale/lsp/response.vim b/autoload/ale/lsp/response.vim
index ab3c503d..939a8997 100644
--- a/autoload/ale/lsp/response.vim
+++ b/autoload/ale/lsp/response.vim
@@ -29,7 +29,6 @@ function! ale#lsp#response#ReadDiagnostics(response) abort
         let l:severity = get(l:diagnostic, 'severity', 0)
         let l:loclist_item = {
         \   'text': l:diagnostic.message,
-        \   'detail': printf("[%s] %s", l:diagnostic.source, l:diagnostic.message),
         \   'type': 'E',
         \   'lnum': l:diagnostic.range.start.line + 1,
         \   'col': l:diagnostic.range.start.character + 1,
@@ -51,6 +50,10 @@ function! ale#lsp#response#ReadDiagnostics(response) abort
             let l:loclist_item.nr = l:diagnostic.code
         endif
 
+        if has_key(l:diagnostic, 'source')
+           let l:loclist_item.detail = printf("[%s] %s", l:diagnostic.source, l:diagnostic.message)
+        endif
+
         call add(l:loclist, l:loclist_item)
     endfor