diff --git a/src/rospkg/rospack.py b/src/rospkg/rospack.py
index ff32ae94..252f6812 100644
--- a/src/rospkg/rospack.py
+++ b/src/rospkg/rospack.py
@@ -402,7 +402,6 @@ def get_licenses(self, pkg_name, implicit=True):
         @rtype { k, [d] }
         @raise ResourceNotFound
         """
-        MSG_LICENSE_NOTFOUND_SYSPKG = "ERR"
         license_dict = defaultdict(list)
 
         self.get_depends(name=pkg_name, implicit=implicit)
@@ -414,7 +413,7 @@ def get_licenses(self, pkg_name, implicit=True):
         # Traverse for Non-ROS, system packages
         pkgnames_rosdep = self.get_rosdeps(package=pkg_name, implicit=implicit)
         for pkgname_rosdep in pkgnames_rosdep:
-            license_dict[MSG_LICENSE_NOTFOUND_SYSPKG].append(pkgname_rosdep)
+            license_dict[None].append(pkgname_rosdep)
 
         # Sort pkg names in each license
         for list_key in license_dict.values():