diff --git a/src/fw-iso.c b/src/fw-iso.c
index 9e66fff..8c0dc6b 100644
--- a/src/fw-iso.c
+++ b/src/fw-iso.c
@@ -260,6 +260,7 @@ int fw_iso_xmit_write(raw1394handle_t handle, unsigned char *data,
 	struct fw_cdev_queue_iso queue_iso;
 	struct fw_cdev_start_iso start_iso;
 	struct fw_cdev_iso_packet *p;
+	int retval;
 
 	if (len > fwhandle->iso.max_packet_size) {
 		errno = EINVAL;
@@ -284,10 +285,10 @@ int fw_iso_xmit_write(raw1394handle_t handle, unsigned char *data,
 		start_iso.cycle  = fwhandle->iso.start_on_cycle;
 		start_iso.handle = 0;
 
-		len = ioctl(fwhandle->iso.fd,
+		retval = ioctl(fwhandle->iso.fd,
 			       FW_CDEV_IOC_START_ISO, &start_iso);
-		if (len < 0)
-			return len;
+		if (retval < 0)
+			return retval;
 	}
 
 	return 0;
diff --git a/src/fw.c b/src/fw.c
index 9c0c2e9..a4bbf3c 100644
--- a/src/fw.c
+++ b/src/fw.c
@@ -1176,14 +1176,14 @@ fw_lock(raw1394handle_t handle, nodeid_t node, nodeaddr_t addr,
 	     quadlet_t *result)
 {
 	quadlet_t buffer[2];
-	size_t length;
+	ssize_t length;
 
 	length = setup_lock(extcode, data, arg, buffer);
 	if (length < 0)
 		return length;
 
 	return send_request_sync(handle, 16 + extcode, node, addr,
-				 length, buffer, result);
+				 (size_t) length, buffer, result);
 }
 
 int
@@ -1192,14 +1192,14 @@ fw_lock64(raw1394handle_t handle, nodeid_t node, nodeaddr_t addr,
 	       octlet_t *result)
 {
 	octlet_t buffer[2];
-	size_t length;
+	ssize_t length;
 
 	length = setup_lock64(extcode, data, arg, buffer);
 	if (length < 0)
 		return length;
 
 	return send_request_sync(handle, 16 + extcode, node, addr,
-				 length, buffer, result);
+				 (size_t) length, buffer, result);
 }
 
 int