diff --git a/hgext/sparse.py b/hgext/sparse.py
--- a/hgext/sparse.py
+++ b/hgext/sparse.py
@@ -75,7 +75,6 @@ certain files::
 from __future__ import absolute_import
 
 from mercurial.i18n import _
-from mercurial.node import nullid
 from mercurial import (
     cmdutil,
     commands,
@@ -448,23 +447,13 @@ def _config(ui, repo, pats, opts, includ
 
 def _import(ui, repo, files, opts, force=False):
     with repo.wlock():
-        # load union of current active profile
-        revs = [repo.changelog.rev(node) for node in
-                repo.dirstate.parents() if node != nullid]
-
         # read current configuration
         raw = repo.vfs.tryread('sparse')
         oincludes, oexcludes, oprofiles = sparse.parseconfig(ui, raw)
         includes, excludes, profiles = map(
                 set, (oincludes, oexcludes, oprofiles))
 
-        # all active rules
-        aincludes, aexcludes, aprofiles = set(), set(), set()
-        for rev in revs:
-            rincludes, rexcludes, rprofiles = sparse.patternsforrev(repo, rev)
-            aincludes.update(rincludes)
-            aexcludes.update(rexcludes)
-            aprofiles.update(rprofiles)
+        aincludes, aexcludes, aprofiles = sparse.activeconfig(repo)
 
         # import rules on top; only take in rules that are not yet
         # part of the active rules.
diff --git a/mercurial/sparse.py b/mercurial/sparse.py
--- a/mercurial/sparse.py
+++ b/mercurial/sparse.py
@@ -124,15 +124,26 @@ def patternsforrev(repo, rev):
 
     return includes, excludes, profiles
 
-def activeprofiles(repo):
+def activeconfig(repo):
+    """Determine the active sparse config rules.
+
+    Rules are constructed by reading the current sparse config and bringing in
+    referenced profiles from parents of the working directory.
+    """
     revs = [repo.changelog.rev(node) for node in
             repo.dirstate.parents() if node != nullid]
 
-    profiles = set()
+    allincludes = set()
+    allexcludes = set()
+    allprofiles = set()
+
     for rev in revs:
-        profiles.update(patternsforrev(repo, rev)[2])
+        includes, excludes, profiles = patternsforrev(repo, rev)
+        allincludes |= includes
+        allexcludes |= excludes
+        allprofiles |= set(profiles)
 
-    return profiles
+    return allincludes, allexcludes, allprofiles
 
 def configsignature(repo, includetemp=True):
     """Obtain the signature string for the current sparse configuration.
@@ -361,7 +372,7 @@ def filterupdatesactions(repo, wctx, mct
         for file, flags, msg in actions:
             dirstate.normal(file)
 
-    profiles = activeprofiles(repo)
+    profiles = activeconfig(repo)[2]
     changedprofiles = profiles & files
     # If an active profile changed during the update, refresh the checkout.
     # Don't do this during a branch merge, since all incoming changes should