diff --git a/autoload/ale/engine.vim b/autoload/ale/engine.vim
index 8c3d4c73..a21eecdd 100644
--- a/autoload/ale/engine.vim
+++ b/autoload/ale/engine.vim
@@ -76,6 +76,8 @@ function! ale#engine#InitBufferInfo(buffer) abort
     return 0
 endfunction
 
+" This function is documented and part of the public API.
+"
 " Return 1 if ALE is busy checking a given buffer
 function! ale#engine#IsCheckingBuffer(buffer) abort
     let l:info = get(g:ale_buffer_info, a:buffer, {})
diff --git a/doc/ale.txt b/doc/ale.txt
index 999d2af4..fd3e4897 100644
--- a/doc/ale.txt
+++ b/doc/ale.txt
@@ -1907,6 +1907,13 @@ ale#engine#GetLoclist(buffer)                         *ale#engine#GetLoclist()*
   be copied before applying |map()| or |filter()|.
 
 
+ale#engine#IsCheckingBuffer(buffer)             *ale#engine#IsCheckingBuffer()*
+
+  Given a buffer number, returns `1` when ALE is busy checking that buffer.
+
+  This function can be used for status lines, tab names, etc.
+
+
 ale#engine#ManageFile(buffer, filename)               *ale#engine#ManageFile()*
 
   Given a buffer number for a buffer currently running some linting tasks