diff --git a/doc/man-pages/pod1/fs_flushall.pod b/doc/man-pages/pod1/fs_flushall.pod
index 38a9144611..cccbcd4552 100644
--- a/doc/man-pages/pod1/fs_flushall.pod
+++ b/doc/man-pages/pod1/fs_flushall.pod
@@ -42,7 +42,7 @@ as follows:
 
 =head1 PRIVILEGE REQUIRED
 
-No special privileges are required for this command.
+The issuer must be logged in as the local superuser C<root>.
 
 =head1 SEE ALSO
 
diff --git a/src/afs/afs_pioctl.c b/src/afs/afs_pioctl.c
index 17b9e0860e..1b304b5481 100644
--- a/src/afs/afs_pioctl.c
+++ b/src/afs/afs_pioctl.c
@@ -3680,6 +3680,7 @@ DECL_PIOCTL(PFlushVolumeData)
  *
  * \retval EINVAL	Error if some of the standard args aren't set
  * \retval EIO		Error if the afs daemon hasn't started yet
+ * \retval EACCES	Error if the user doesn't have super-user credentials
  *
  * \post
  * 	Flush all cached contents.  Exactly what stays and what
@@ -3697,6 +3698,9 @@ DECL_PIOCTL(PFlushAllVolumeData)
     if (!afs_resourceinit_flag)	/* afs daemons haven't started yet */
 	return EIO;		/* Inappropriate ioctl for device */
 
+    if (!afs_osi_suser(*acred))
+	return EACCES;
+
     return FlushVolumeData(NULL, *acred);
 }