diff --git a/NEWS b/NEWS
index 10398beb..8ead2b7f 100644
--- a/NEWS
+++ b/NEWS
@@ -15,6 +15,7 @@
       generous donation which made this behavior possible)
     * IMPORTANT: ctrl-x/a never take possible negative URLs into account, it was just
       too unpredictable
+    * add 'shell' and 'shellcmdflag' options
     * :tabprevious, :bprevious, :tabnext, :bnext and friends now accept a prefix count
     * add :comclear and :delcommand
     * add a special version to :hardcopy to skip the Print dialog
diff --git a/content/io.js b/content/io.js
index d64ca700..df8fe47d 100644
--- a/content/io.js
+++ b/content/io.js
@@ -41,6 +41,34 @@ liberator.IO = function () //{{{
     var extname = liberator.config.name.toLowerCase(); // "vimperator" or "muttator"
     var lastRunCommand = ""; // updated whenever the users runs a command with :!
 
+    /////////////////////////////////////////////////////////////////////////////}}}
+    ////////////////////// OPTIONS ////////////////////////////////////////////////
+    /////////////////////////////////////////////////////////////////////////////{{{
+
+    var shell, shellcmdflag;
+
+    if (WINDOWS)
+    {
+        shell = "cmd.exe";
+        // TODO: does setting 'shell' to "something containing sh"
+        // automatically update 'shellcmdflag' on Windows in Vim?
+        shellcmdflag = "/c";
+    }
+    else
+    {
+        shell = environmentService.get("SHELL") || "sh";
+        shellcmdflag = "-c";
+    }
+
+    // TODO: setter should expand environment variables
+    liberator.options.add(["shell", "sh"],
+        "Shell to use for executing :! and :run commands",
+        "string", shell);
+
+    liberator.options.add(["shellcmdflag", "shcf"],
+        "Flag passed to shell when executing :! and :run commands",
+        "string", shellcmdflag);
+
     /////////////////////////////////////////////////////////////////////////////}}}
     ////////////////////// COMMANDS ////////////////////////////////////////////////
     /////////////////////////////////////////////////////////////////////////////{{{
@@ -507,7 +535,6 @@ lookup:
 
         // when https://bugzilla.mozilla.org/show_bug.cgi?id=68702 is fixed
         // is fixed, should use that instead of a tmpfile
-        // TODO: add shell/shellcmdflag options to replace "sh" and "-c"
         system: function (str, input)
         {
             var fileout = ioManager.createTempFile();
@@ -527,11 +554,8 @@ lookup:
                 command += " < \"" + filein.path.replace('"', '\\"') + "\"";
             }
 
-            var res;
-            if (WINDOWS)
-                res = ioManager.run("cmd.exe", ["/C", command], true);
-            else
-                res = ioManager.run("sh", ["-c", command], true);
+            // FIXME: why is this return value being ignored?
+            var res = ioManager.run(liberator.options["shell"], [liberator.options["shellcmdflag"], command], true);
 
             var output = ioManager.readFile(fileout);
             fileout.remove(false);
diff --git a/locale/en-US/options.txt b/locale/en-US/options.txt
index 3bd74cea..234e9c72 100644
--- a/locale/en-US/options.txt
+++ b/locale/en-US/options.txt
@@ -528,13 +528,29 @@ value can be reset to half the window height with [c]:set scroll=0[c].
 ____
 
 
-|\'nosmd'| |\'noshowmode'| |\'smd'| |\'showmode'|
-||'showmode' 'smd'|| boolean (default: on)
+|\'shell'| |\'sh'|
+||'shell' 'sh'|| string (default: on)
 ____
 Show the current mode in the command line.
 ____
 
 
+|\'shellcmdflag'| |\'shcf'|
+||'shellcmdflag' 'shcf'|| string (default: $SHELL or "sh", Win32: "cmd.exe")
+____
+Shell to use for executing :! and :run commands.
+____
+
+
+|\'nosmd'| |\'noshowmode'| |\'smd'| |\'showmode'|
+||'showmode' 'smd'|| boolean (default: "-c", Win32: "/c")
+____
+Flag passed to shell when executing :! and :run commands.
+
+E.g. bash -c gvim
+____
+
+
 |\'ssli'| |\'showstatuslinks'|
 ||'showstatuslinks' 'ssli'|| number (default: 1)
 ____