diff --git a/drivers/staging/comedi/drivers/das1800.c b/drivers/staging/comedi/drivers/das1800.c
index d3aca976ee4c6bc153dd38a1be22cf4aa0919328..52a8c5b8234c37300978f1084fc356ca5f9066fe 100644
--- a/drivers/staging/comedi/drivers/das1800.c
+++ b/drivers/staging/comedi/drivers/das1800.c
@@ -225,7 +225,7 @@ enum das1800_boardid {
 struct das1800_board {
 	const char *name;
 	unsigned char id;
-	int ai_speed;		/* max conversion period in nanoseconds */
+	unsigned int ai_speed;
 	unsigned int is_01_series:1;
 };