diff -up sudo-1.7.4p4/configure.in.getgrouplist sudo-1.7.4p4/configure.in
--- sudo-1.7.4p4/configure.in.getgrouplist	2011-01-11 10:45:49.170262147 +0100
+++ sudo-1.7.4p4/configure.in	2011-01-11 10:45:49.176261407 +0100
@@ -1913,7 +1913,7 @@ AC_FUNC_GETGROUPS
 AC_CHECK_FUNCS(strchr strrchr memchr memcpy memset sysconf tzset \
 	       strftime setrlimit initgroups getgroups fstat gettimeofday \
 	       regcomp setlocale getaddrinfo setenv vhangup \
-	       mbr_check_membership setrlimit64)
+	       mbr_check_membership setrlimit64 getgrouplist)
 AC_CHECK_FUNCS(getline, [], [
     AC_LIBOBJ(getline)
     AC_CHECK_FUNCS(fgetln)
diff -up sudo-1.7.4p4/pwutil.c.getgrouplist sudo-1.7.4p4/pwutil.c
--- sudo-1.7.4p4/pwutil.c.getgrouplist	2010-08-06 15:44:30.000000000 +0200
+++ sudo-1.7.4p4/pwutil.c	2011-01-11 11:42:16.771282451 +0100
@@ -628,5 +628,26 @@ user_in_group(pw, group)
     }
 #endif /* HAVE_MBR_CHECK_MEMBERSHIP */
 
+#ifdef HAVE_GETGROUPLIST
+    if (user_ngroups >= 0 &&
+	strcmp(pw->pw_name, list_pw ? list_pw->pw_name : user_name) == 0)
+    {
+	gid_t *grouplist, grouptmp;
+	int n_groups, i;
+	n_groups = 1;
+
+	if (getgrouplist(user_name, user_gid, &grouptmp, &n_groups) == -1) {
+	    grouplist = (gid_t *) emalloc(sizeof(gid_t) * (n_groups + 1));
+	    if (getgrouplist(user_name, user_gid, grouplist, &n_groups) > 0)
+		for (i = 0; i < n_groups; i++)
+		    if (grouplist[i] == grp->gr_gid) {
+			free(grouplist);
+			return(TRUE);
+		    }
+	    free(grouplist);
+	}
+    }
+#endif /* HAVE_GETGROUPLIST */
+
     return(FALSE);
 }