diff --git a/firmware/ice40-riscv/icE1usb/e1.c b/firmware/ice40-riscv/icE1usb/e1.c
index 0e14b6f..17be75d 100644
--- a/firmware/ice40-riscv/icE1usb/e1.c
+++ b/firmware/ice40-riscv/icE1usb/e1.c
@@ -191,7 +191,7 @@
 }
 
 static unsigned int
-e1f_frame_read(struct e1_fifo *fifo, unsigned int *ofs, int max_frames)
+e1f_frame_read(struct e1_fifo *fifo, unsigned int *ofs, unsigned int max_frames)
 {
 	unsigned int lu, le;