diff --git a/sys/dev/mmc/mmc.c b/sys/dev/mmc/mmc.c
index 74d0549ca49..071c238374d 100644
--- a/sys/dev/mmc/mmc.c
+++ b/sys/dev/mmc/mmc.c
@@ -1920,7 +1920,7 @@ child_common:
 			if (child != NULL) {
 				device_set_ivars(child, ivar);
 				sc->child_list = realloc(sc->child_list,
-				    sizeof(device_t) * sc->child_count + 1,
+				    sizeof(device_t) * (sc->child_count + 1),
 				    M_DEVBUF, M_WAITOK);
 				sc->child_list[sc->child_count++] = child;
 			} else