diff --git a/drivers/net/fm/fm.h b/drivers/net/fm/fm.h
index 43de114..316e06e 100644
--- a/drivers/net/fm/fm.h
+++ b/drivers/net/fm/fm.h
@@ -143,6 +143,7 @@
 #define MAX_RXBUF_LOG2		11
 #define MAX_RXBUF_LEN		(1 << MAX_RXBUF_LOG2)
 
-#define PORT_IS_ENABLED(port)	fm_info[fm_port_to_index(port)].enabled
+#define PORT_IS_ENABLED(port)	(fm_port_to_index(port) == -1 ? \
+	0 : fm_info[fm_port_to_index(port)].enabled)
 
 #endif /* __FM_H__ */
diff --git a/drivers/net/fm/init.c b/drivers/net/fm/init.c
index cd787f4..ff04695 100644
--- a/drivers/net/fm/init.c
+++ b/drivers/net/fm/init.c
@@ -147,6 +147,9 @@
 {
 	int i = fm_port_to_index(port);
 
+	if (i == -1)
+		return;
+
 	fm_info[i].enabled = 0;
 	fman_disable_port(port);
 }
@@ -155,6 +158,9 @@
 {
 	int i = fm_port_to_index(port);
 
+	if (i == -1)
+		return;
+
 	fm_info[i].enabled = 1;
 	fman_enable_port(port);
 }