diff --git a/contrib/pam_zfs_key/pam_zfs_key.c b/contrib/pam_zfs_key/pam_zfs_key.c
index d87384cee6..878e65a8e6 100644
--- a/contrib/pam_zfs_key/pam_zfs_key.c
+++ b/contrib/pam_zfs_key/pam_zfs_key.c
@@ -219,6 +219,8 @@ pw_clear(pam_handle_t *pamh)
 static void
 destroy_pw(pam_handle_t *pamh, void *data, int errcode)
 {
+	(void) pamh, (void) errcode;
+
 	if (data != NULL) {
 		pw_free((pw_password_t *)data);
 	}
@@ -638,6 +640,8 @@ PAM_EXTERN int
 pam_sm_authenticate(pam_handle_t *pamh, int flags,
     int argc, const char **argv)
 {
+	(void) flags, (void) argc, (void) argv;
+
 	if (pw_fetch_lazy(pamh) == NULL) {
 		return (PAM_AUTH_ERR);
 	}
@@ -650,6 +654,7 @@ PAM_EXTERN int
 pam_sm_setcred(pam_handle_t *pamh, int flags,
     int argc, const char **argv)
 {
+	(void) pamh, (void) flags, (void) argc, (void) argv;
 	return (PAM_SUCCESS);
 }
 
@@ -737,6 +742,8 @@ PAM_EXTERN int
 pam_sm_open_session(pam_handle_t *pamh, int flags,
     int argc, const char **argv)
 {
+	(void) flags;
+
 	if (geteuid() != 0) {
 		pam_syslog(pamh, LOG_ERR,
 		    "Cannot zfs_mount when not being root.");
@@ -791,6 +798,8 @@ PAM_EXTERN int
 pam_sm_close_session(pam_handle_t *pamh, int flags,
     int argc, const char **argv)
 {
+	(void) flags;
+
 	if (geteuid() != 0) {
 		pam_syslog(pamh, LOG_ERR,
 		    "Cannot zfs_mount when not being root.");