diff --git a/drivers/s390/cio/vfio_ccw_cp.c b/drivers/s390/cio/vfio_ccw_cp.c
index 9cddc1288059..a7b9dfd5b464 100644
--- a/drivers/s390/cio/vfio_ccw_cp.c
+++ b/drivers/s390/cio/vfio_ccw_cp.c
@@ -161,7 +161,7 @@ static inline void pfn_array_idal_create_words(
 	idaws[0] += pa->pa_iova & (PAGE_SIZE - 1);
 }
 
-void convert_ccw0_to_ccw1(struct ccw1 *source, unsigned long len)
+static void convert_ccw0_to_ccw1(struct ccw1 *source, unsigned long len)
 {
 	struct ccw0 ccw0;
 	struct ccw1 *pccw1 = source;