diff --git a/bumblebee/output.py b/bumblebee/output.py
index 1f494ad..cfdc88b 100644
--- a/bumblebee/output.py
+++ b/bumblebee/output.py
@@ -1,8 +1,7 @@
 import os
-import shlex
 import inspect
 import threading
-import subprocess
+import bumblebee.util
 
 def output(args):
     import bumblebee.outputs.i3
@@ -57,8 +56,7 @@ class Command(object):
                 cmd(self._event, self._widget)
             else:
                 c = cmd.format(*args, **kwargs)
-                DEVNULL = open(os.devnull, 'wb')
-                subprocess.Popen(shlex.split(c), stdout=DEVNULL, stderr=DEVNULL)
+                bumblebee.util.execute(c, False)
 
 class Output(object):
     def __init__(self, config):
@@ -103,14 +101,14 @@ class Output(object):
     def wait(self):
         self._wait.wait(self._config.parameter("interval", 1))
 
-    def start(self):
-        pass
-
     def draw(self, widgets, theme):
         if not type(widgets) is list:
             widgets = [ widgets ]
         self._draw(widgets, theme)
 
+    def start(self):
+        pass
+
     def _draw(self, widgets, theme):
         pass
 
diff --git a/bumblebee/outputs/i3.py b/bumblebee/outputs/i3.py
index c0800dd..e287c6c 100644
--- a/bumblebee/outputs/i3.py
+++ b/bumblebee/outputs/i3.py
@@ -51,10 +51,6 @@ class Output(bumblebee.output.Output):
                     "separator_block_width": 0,
                 })
 
-            sep = theme.default_separators(widget)
-            sep = sep if sep else False
-            width = theme.separator_block_width(widget)
-            width = width if width else 0
             self._data.append({
                 u"full_text": " {} {} {}".format(
                     theme.prefix(widget),
@@ -65,8 +61,8 @@ class Output(bumblebee.output.Output):
                 "background": theme.background(widget),
                 "name": widget.module(),
                 "instance": widget.instance(),
-                "separator": sep,
-                "separator_block_width": width,
+                "separator": theme.default_separators(widget, False),
+                "separator_block_width": theme.separator_block_width(widget, 0),
             })
             theme.next_widget()
 
diff --git a/bumblebee/theme.py b/bumblebee/theme.py
index cd8d860..2f7d5c7 100644
--- a/bumblebee/theme.py
+++ b/bumblebee/theme.py
@@ -89,8 +89,8 @@ class Theme:
     def separator(self, widget):
         return self._get(widget, "separator")
 
-    def default_separators(self, widget):
-        return self._get(widget, "default-separators")
+    def default_separators(self, widget, default):
+        return self._get(widget, "default-separators", default)
 
     def separator_color(self, widget):
         return self.background(widget)
@@ -98,8 +98,8 @@ class Theme:
     def separator_background(self, widget):
         return self._background[1]
 
-    def separator_block_width(self, widget):
-        return self._get(widget, "separator-block-width")
+    def separator_block_width(self, widget, default):
+        return self._get(widget, "separator-block-width", default)
 
     def _get(self, widget, name, default = None):
         module = widget.module()
diff --git a/bumblebee/util.py b/bumblebee/util.py
index c38bb79..3a6a60c 100644
--- a/bumblebee/util.py
+++ b/bumblebee/util.py
@@ -21,12 +21,13 @@ def durationfmt(duration):
 
     return res
 
-def execute(cmd):
+def execute(cmd, wait=True):
     args = shlex.split(cmd)
     p = subprocess.Popen(args, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
-    out, err = p.communicate()
 
-    if p.returncode != 0:
-        raise RuntimeError("{} exited with {}".format(cmd, p.returncode))
-
-    return out.decode("utf-8")
+    if wait:
+        out, err = p.communicate()
+        if p.returncode != 0:
+            raise RuntimeError("{} exited with {}".format(cmd, p.returncode))
+        return out.decode("utf-8")
+    return None