diff --git a/core/divelist.c b/core/divelist.c
index a7e52a0a7..a92eb82e9 100644
--- a/core/divelist.c
+++ b/core/divelist.c
@@ -43,6 +43,8 @@ void get_dive_gas(const struct dive *dive, int *o2_p, int *he_p, int *o2max_p)
 			continue;
 		if (cyl->cylinder_use == OXYGEN)
 			continue;
+		if (cyl->cylinder_use == NOT_USED)
+			continue;
 		if (o2 > maxo2)
 			maxo2 = o2;
 		if (he > maxhe)