diff --git a/autoload/gitgutter/utility.vim b/autoload/gitgutter/utility.vim
index 319cf6d..9e13a8b 100644
--- a/autoload/gitgutter/utility.vim
+++ b/autoload/gitgutter/utility.vim
@@ -190,12 +190,14 @@ endfunction
 
 function! gitgutter#utility#use_known_shell() abort
   if has('unix')
-    let s:shell = &shell
-    let s:shellcmdflag = &shellcmdflag
-    let s:shellredir = &shellredir
-    let &shell = 'sh'
-    set shellcmdflag=-c
-    set shellredir=>%s\ 2>&1
+    if &shell !=# 'sh'
+      let s:shell = &shell
+      let s:shellcmdflag = &shellcmdflag
+      let s:shellredir = &shellredir
+      let &shell = 'sh'
+      set shellcmdflag=-c
+      set shellredir=>%s\ 2>&1
+    endif
   endif
 endfunction
 
diff --git a/test/testHunkStage.vim b/test/testHunkStage.vim
index 6f818fb..6acf19e 100644
--- a/test/testHunkStage.vim
+++ b/test/testHunkStage.vim
@@ -1,7 +1,13 @@
 source helper.vim
 call Setup()
 
+set shell=foo
+
 normal 5Gi*
 execute 'GitGutterStageHunk'
+
+call assert_equal('foo', &shell)  " NOTE: current test runner ignores v:errors so this line has no effect
+
+set shell=/bin/bash
 call DumpSigns('hunkStageSigns')
 call DumpGitDiffStaged('hunkStageGitDiff')
diff --git a/test/testHunkUndo.vim b/test/testHunkUndo.vim
index 9d187a7..2afc8fa 100644
--- a/test/testHunkUndo.vim
+++ b/test/testHunkUndo.vim
@@ -1,7 +1,12 @@
 source helper.vim
 call Setup()
 
+set shell=foo
+
 normal 5Gi*
 execute 'GitGutterUndoHunk'
+
+call assert_equal('foo', &shell)  " NOTE: current test runner ignores v:errors so this line has no effect
+set shell=/bin/bash
 call DumpSigns('hunkUndoSigns')
 call DumpGitDiffStaged('hunkUndoGitDiff')