diff --git a/src/potion.c b/src/potion.c
index 25989fff5..9d5a89fc8 100644
--- a/src/potion.c
+++ b/src/potion.c
@@ -2495,7 +2495,8 @@ potion_dip(struct obj *obj, struct obj *potion)
         useup(potion); /* now gone */
         /* Mixing potions is dangerous...
            KMH, balance patch -- acid is particularly unstable */
-        if (obj->cursed || obj->otyp == POT_ACID || !rn2(10)) {
+        if (obj->cursed || obj->otyp == POT_ACID
+            || (obj->otyp == POT_OIL && obj->lamplit) || !rn2(10)) {
             /* it would be better to use up the whole stack in advance
                of the message, but we can't because we need to keep it
                around for potionbreathe() [and we can't set obj->in_use