diff --git a/libserialport.h.in b/libserialport.h.in
index 1dd4715..24e1a40 100644
--- a/libserialport.h.in
+++ b/libserialport.h.in
@@ -415,7 +415,7 @@ char *sp_get_port_name(const struct sp_port *port);
  *
  * @since 0.1.1
  */
-char *sp_get_port_description(struct sp_port *port);
+char *sp_get_port_description(const struct sp_port *port);
 
 /**
  * Get the transport type used by a port.
diff --git a/serialport.c b/serialport.c
index 272bdf6..074534e 100644
--- a/serialport.c
+++ b/serialport.c
@@ -126,7 +126,7 @@ SP_API char *sp_get_port_name(const struct sp_port *port)
 	RETURN_STRING(port->name);
 }
 
-SP_API char *sp_get_port_description(struct sp_port *port)
+SP_API char *sp_get_port_description(const struct sp_port *port)
 {
 	TRACE("%p", port);