diff --git a/ifupdown/networkinterfaces.py b/ifupdown/networkinterfaces.py
index bc7749d..9a2f9a8 100644
--- a/ifupdown/networkinterfaces.py
+++ b/ifupdown/networkinterfaces.py
@@ -60,8 +60,11 @@ class networkInterfaces():
         self.interfacesfileiobuf = interfacesfileiobuf
         self.interfacesfileformat = interfacesfileformat
         self._filestack = [self.interfacesfile]
-        self._template_engine = templateEngine(template_engine,
-                                    template_lookuppath)
+
+        self._template_engine = None
+        self._template_engine_name = template_engine
+        self._template_engine_path = template_lookuppath
+
         self._currentfile_has_template = False
         self._ws_split_regex = re.compile(r'[\s\t]\s*')
 
@@ -385,22 +388,25 @@ class networkInterfaces():
     def read_filedata(self, filedata):
         self._currentfile_has_template = False
         # run through template engine
-        try:
-            rendered_filedata = self._template_engine.render(filedata)
-            if rendered_filedata is filedata:
-                self._currentfile_has_template = False
-            else:
-                self._currentfile_has_template = True
-        except Exception, e:
-            self._parse_error(self._currentfile, -1,
-                    'failed to render template (%s). ' %str(e) +
-                    'Continue without template rendering ...')
-            rendered_filedata = None
-            pass
-        if rendered_filedata:
-            self.process_interfaces(rendered_filedata)
-        else:
-            self.process_interfaces(filedata)
+        if filedata and '%' in filedata:
+            try:
+                self._template_engine = templateEngine(
+                    self._template_engine_name,
+                    self._template_engine_path)
+                rendered_filedata = self._template_engine.render(filedata)
+                if rendered_filedata is filedata:
+                    self._currentfile_has_template = False
+                else:
+                    self._currentfile_has_template = True
+            except Exception, e:
+                self._parse_error(self._currentfile, -1,
+                                  'failed to render template (%s). Continue without template rendering ...'
+                                  % str(e))
+                rendered_filedata = None
+            if rendered_filedata:
+                self.process_interfaces(rendered_filedata)
+                return
+        self.process_interfaces(filedata)
 
     def read_file(self, filename, fileiobuf=None):
         if fileiobuf: