diff --git a/autoload/ale/fixers/isort.vim b/autoload/ale/fixers/isort.vim
index ba95bb10..a640d233 100644
--- a/autoload/ale/fixers/isort.vim
+++ b/autoload/ale/fixers/isort.vim
@@ -29,6 +29,7 @@ function! ale#fixers#isort#Fix(buffer) abort
     return {
     \   'cwd': '%s:h',
     \   'command': ale#Escape(l:executable) . l:exec_args
+    \   . ale#Pad('--filename %s')
     \   . (!empty(l:options) ? ' ' . l:options : '') . ' -',
     \}
 endfunction
diff --git a/test/fixers/test_isort_fixer_callback.vader b/test/fixers/test_isort_fixer_callback.vader
index 9e112c03..8bfe1238 100644
--- a/test/fixers/test_isort_fixer_callback.vader
+++ b/test/fixers/test_isort_fixer_callback.vader
@@ -18,7 +18,7 @@ Execute(The isort callback should return the correct default values):
   AssertEqual
   \ {
   \   'cwd': '%s:h',
-  \   'command': ale#Escape(ale#path#Simplify(g:dir . '/../test-files/python/with_virtualenv/env/' . b:bin_dir . '/isort')) . ' -',
+  \   'command': ale#Escape(ale#path#Simplify(g:dir . '/../test-files/python/with_virtualenv/env/' . b:bin_dir . '/isort')) . ' --filename %s' . ' -',
   \ },
   \ ale#fixers#isort#Fix(bufnr(''))
 
@@ -34,7 +34,7 @@ Execute(The isort callback should respect custom options):
   \ {
   \   'cwd': '%s:h',
   \   'command': ale#Escape(ale#path#Simplify(g:dir . '/../test-files/python/with_virtualenv/env/' . b:bin_dir . '/isort'))
-  \     . ' --multi-line=3 --trailing-comma -',
+  \     . ' --filename %s' . ' --multi-line=3 --trailing-comma -',
   \ },
   \ ale#fixers#isort#Fix(bufnr(''))
 
@@ -46,6 +46,6 @@ Execute(Pipenv is detected when python_isort_auto_pipenv is set):
   AssertEqual
   \ {
   \   'cwd': '%s:h',
-  \   'command': ale#Escape('pipenv') . ' run isort -'
+  \   'command': ale#Escape('pipenv') . ' run isort' . ' --filename %s' . ' -'
   \ },
   \ ale#fixers#isort#Fix(bufnr(''))