diff --git a/modules/pam_namespace/pam_namespace.8.xml b/modules/pam_namespace/pam_namespace.8.xml
index 0433f0f..f0ebe2c 100644
--- a/modules/pam_namespace/pam_namespace.8.xml
+++ b/modules/pam_namespace/pam_namespace.8.xml
@@ -52,6 +52,9 @@
       <arg choice="opt">
         use_default_context
       </arg>
+      <arg choice="opt">
+        mount_private
+      </arg>
     </cmdsynopsis>
   </refsynopsisdiv>
 
@@ -234,6 +237,21 @@
         </listitem>
       </varlistentry>
 
+      <varlistentry>
+        <term>
+          <option>mount_private</option>
+        </term>
+        <listitem>
+          <para>
+	    This option should be used on systems where the / mount point and
+	    its submounts are made shared (for example with a
+	    <command>mount --make-rshared /</command> command).
+	    The module will make the polyinstantiated directory mount points
+	    private.
+          </para>
+        </listitem>
+      </varlistentry>
+
     </variablelist>
   </refsect1>
 
diff --git a/modules/pam_namespace/pam_namespace.c b/modules/pam_namespace/pam_namespace.c
index c47599e..d5a2d78 100644
--- a/modules/pam_namespace/pam_namespace.c
+++ b/modules/pam_namespace/pam_namespace.c
@@ -1003,7 +1003,7 @@ static int protect_mount(int dfd, const char *path, struct instance_data *idata)
 	return 0;
 }
 
-static int protect_dir(const char *path, mode_t mode, int do_mkdir,
+static int protect_dir(const char *path, mode_t mode, int do_mkdir, int always,
 	struct instance_data *idata)
 {
 	char *p = strdup(path);
@@ -1082,7 +1082,7 @@ static int protect_dir(const char *path, mode_t mode, int do_mkdir,
 		}
 	}
 
-	if (flags & O_NOFOLLOW) { 
+	if ((flags & O_NOFOLLOW) || always) { 
 		/* we are inside user-owned dir - protect */
 		if (protect_mount(rv, p, idata) == -1) {
 			save_errno = errno;
@@ -1124,7 +1124,7 @@ static int check_inst_parent(char *ipath, struct instance_data *idata)
 	if (trailing_slash)
 		*trailing_slash = '\0';
 
-	dfd = protect_dir(inst_parent, 0, 1, idata);
+	dfd = protect_dir(inst_parent, 0, 1, 0, idata);
 
 	if (dfd == -1 || fstat(dfd, &instpbuf) < 0) {
 		pam_syslog(idata->pamh, LOG_ERR,
@@ -1259,7 +1259,7 @@ static int create_polydir(struct polydir_s *polyptr,
     }
 #endif
 
-    rc = protect_dir(dir, mode, 1, idata);
+    rc = protect_dir(dir, mode, 1, idata->flags & PAMNS_MOUNT_PRIVATE, idata);
     if (rc == -1) {
             pam_syslog(idata->pamh, LOG_ERR,
                        "Error creating directory %s: %m", dir);
@@ -1447,7 +1447,7 @@ static int ns_setup(struct polydir_s *polyptr,
         pam_syslog(idata->pamh, LOG_DEBUG,
                "Set namespace for directory %s", polyptr->dir);
 
-    retval = protect_dir(polyptr->dir, 0, 0, idata);
+    retval = protect_dir(polyptr->dir, 0, 0, idata->flags & PAMNS_MOUNT_PRIVATE, idata);
 
     if (retval < 0 && errno != ENOENT) {
 	pam_syslog(idata->pamh, LOG_ERR, "Polydir %s access error: %m",
@@ -1534,6 +1534,22 @@ static int ns_setup(struct polydir_s *polyptr,
         goto error_out;
     }
 
+    if (idata->flags & PAMNS_MOUNT_PRIVATE) {
+        /*
+         * Make the polyinstantiated dir private mount. This depends
+         * on making the dir a mount point in the protect_dir call.
+         */
+        if (mount(polyptr->dir, polyptr->dir, NULL, MS_PRIVATE|MS_REC, NULL) < 0) {
+            pam_syslog(idata->pamh, LOG_ERR, "Error making %s a private mount, %m",
+                       polyptr->dir);
+            goto error_out;
+        }
+        if (idata->flags & PAMNS_DEBUG)
+            pam_syslog(idata->pamh, LOG_DEBUG,
+                      "Polyinstantiated directory %s made as private mount", polyptr->dir);
+
+    }
+
     /*
      * Bind mount instance directory on top of the polyinstantiated
      * directory to provide an instance of polyinstantiated directory
@@ -1964,6 +1980,9 @@ PAM_EXTERN int pam_sm_open_session(pam_handle_t *pamh, int flags UNUSED,
             idata.flags |= PAMNS_USE_DEFAULT_CONTEXT;
             idata.flags |= PAMNS_CTXT_BASED_INST;
         }
+        if (strcmp(argv[i], "mount_private") == 0) {
+            idata.flags |= PAMNS_MOUNT_PRIVATE;
+        }
         if (strcmp(argv[i], "unmnt_remnt") == 0)
             unmnt = UNMNT_REMNT;
         if (strcmp(argv[i], "unmnt_only") == 0)
diff --git a/modules/pam_namespace/pam_namespace.h b/modules/pam_namespace/pam_namespace.h
index da21bd7..7b39068 100644
--- a/modules/pam_namespace/pam_namespace.h
+++ b/modules/pam_namespace/pam_namespace.h
@@ -96,6 +96,7 @@
 #define PAMNS_NO_UNMOUNT_ON_CLOSE  0x00010000 /* no unmount at session close */
 #define PAMNS_USE_CURRENT_CONTEXT  0x00020000 /* use getcon instead of getexeccon */
 #define PAMNS_USE_DEFAULT_CONTEXT  0x00040000 /* use get_default_context instead of getexeccon */
+#define PAMNS_MOUNT_PRIVATE   0x00080000 /* Make the polydir mounts private */
 
 /* polydir flags */
 #define POLYDIR_EXCLUSIVE     0x00000001 /* polyinstatiate exclusively for override uids */