diff --git a/src/deh_soc.c b/src/deh_soc.c
index f23c71970..5b007d4f9 100644
--- a/src/deh_soc.c
+++ b/src/deh_soc.c
@@ -3078,6 +3078,7 @@ void readcupheader(MYFILE *f, cupheader_t *cup)
 					if (cup->cachedlevels[cup->numlevels] == NEXTMAP_INVALID)
 						continue;
 					mapheaderinfo[cup->cachedlevels[cup->numlevels]]->cup = NULL;
+					cup->cachedlevels[cup->numlevels] = NEXTMAP_INVALID;
 				}
 
 				tmp = strtok(word2,",");
@@ -3100,6 +3101,10 @@ void readcupheader(MYFILE *f, cupheader_t *cup)
 					cup->numbonus--;
 					Z_Free(cup->levellist[CUPCACHE_BONUS + cup->numbonus]);
 					cup->levellist[CUPCACHE_BONUS + cup->numbonus] = NULL;
+					if (cup->cachedlevels[CUPCACHE_BONUS + cup->numbonus] == NEXTMAP_INVALID)
+						continue;
+					mapheaderinfo[cup->cachedlevels[CUPCACHE_BONUS + cup->numbonus]]->cup = NULL;
+					cup->cachedlevels[CUPCACHE_BONUS + cup->numbonus] = NEXTMAP_INVALID;
 				}
 
 				tmp = strtok(word2,",");
diff --git a/src/g_game.c b/src/g_game.c
index ab4b6bc9c..1bcbd5555 100644
--- a/src/g_game.c
+++ b/src/g_game.c
@@ -3891,6 +3891,12 @@ static void G_GetNextMap(void)
 						|| (!marathonmode && M_MapLocked(cm+1)))
 						continue;
 
+					// If the map is in multiple cups, only consider the first one valid.
+					if (mapheaderinfo[cm]->cup != cup)
+					{
+						continue;
+					}
+
 					// Grab the first valid after the map you're on
 					if (gettingresult)
 					{
diff --git a/src/p_setup.c b/src/p_setup.c
index 6a1c5c049..0130acc86 100644
--- a/src/p_setup.c
+++ b/src/p_setup.c
@@ -7794,13 +7794,9 @@ UINT8 P_InitMapData(boolean existingmapheaders)
 					if (strcasecmp(cup->levellist[j], name) != 0)
 						continue;
 
-					// Only panic about back-reference for non-bonus material.
-					if (j < MAXLEVELLIST)
-					{
-						if (mapheaderinfo[i]->cup)
-							I_Error("P_InitMapData: Map %s cannot appear in cups multiple times! (First in %s, now in %s)", name, mapheaderinfo[i]->cup->name, cup->name);
+					// Have a map recognise the first cup it's a part of.
+					if (!mapheaderinfo[i]->cup)
 						mapheaderinfo[i]->cup = cup;
-					}
 
 					cup->cachedlevels[j] = i;
 				}