diff --git a/channels/rail/rail_common.c b/channels/rail/rail_common.c
index 902a738c5..b6d69b799 100644
--- a/channels/rail/rail_common.c
+++ b/channels/rail/rail_common.c
@@ -51,9 +51,13 @@ static const char* const RAIL_ORDER_TYPE_STRINGS[] = { "",
 	                                                   "",
 	                                                   "" };
 
-const char* rail_get_order_type_string(BYTE orderType)
+const char* rail_get_order_type_string(UINT16 orderType)
 {
-	return RAIL_ORDER_TYPE_STRINGS[((orderType & 0xF0) >> 3) + (orderType & 0x0F)];
+	UINT32 index = ((orderType & 0xF0) >> 3) + (orderType & 0x0F);
+	if (index >= ARRAYSIZE(RAIL_ORDER_TYPE_STRINGS))
+		return "UNKNOWN";
+
+	return RAIL_ORDER_TYPE_STRINGS[index];
 }
 
 /**
diff --git a/channels/rail/rail_common.h b/channels/rail/rail_common.h
index 6d411ebb1..e13412df9 100644
--- a/channels/rail/rail_common.h
+++ b/channels/rail/rail_common.h
@@ -26,8 +26,6 @@
 
 #include <freerdp/rail.h>
 
-const char* rail_get_order_type_string(BYTE orderType);
-
 #define RAIL_PDU_HEADER_LENGTH 4
 
 /* Fixed length of PDUs, excluding variable lengths */
@@ -72,5 +70,6 @@ UINT rail_read_sysparam_order(wStream* s, RAIL_SYSPARAM_ORDER* sysparam, BOOL ex
 UINT rail_write_sysparam_order(wStream* s, const RAIL_SYSPARAM_ORDER* sysparam,
                                BOOL extendedSpiSupported);
 BOOL rail_is_extended_spi_supported(UINT32 channelsFlags);
+const char* rail_get_order_type_string(UINT16 orderType);
 
 #endif /* FREERDP_CHANNEL_RAIL_COMMON_H */