diff --git a/src/d_iwad.c b/src/d_iwad.c
index 1b2a8d40..a4a37135 100644
--- a/src/d_iwad.c
+++ b/src/d_iwad.c
@@ -854,9 +854,11 @@ void D_GetModeAndMissionByIWADName(const char *name, GameMode_t *mode,
         {
             *mode = iwads[i].mode;
             *mission = iwads[i].mission;
-            break;
+            return;
         }
     }
+    *mode = indetermined;
+    *mission = none;
 }
 
 const char *D_GetIWADDescription(const char *name, GameMode_t mode,
diff --git a/src/d_main.c b/src/d_main.c
index 6b61fb3d..5e03666d 100644
--- a/src/d_main.c
+++ b/src/d_main.c
@@ -1347,13 +1347,19 @@ static void LoadIWadBase(void)
 {
     GameMode_t local_gamemode;
     GameMission_t local_gamemission;
-    D_GetModeAndMissionByIWADName(M_BaseName(wadfiles[0]), &local_gamemode, &local_gamemission);
+    D_GetModeAndMissionByIWADName(M_BaseName(wadfiles[0]), &local_gamemode,
+                                  &local_gamemission);
+
+    if (local_gamemission == none || local_gamemode == indetermined)
+    {
+        return;
+    }
 
     if (local_gamemission < pack_chex)
     {
         W_AddBaseDir("doom-all");
     }
-    else if (local_gamemission == pack_chex || local_gamemission == pack_chex3v)
+    if (local_gamemission == pack_chex || local_gamemission == pack_chex3v)
     {
         W_AddBaseDir("chex-all");
     }
@@ -1361,8 +1367,7 @@ static void LoadIWadBase(void)
     {
         W_AddBaseDir("doom1-all");
     }
-    else if (local_gamemission >= doom2
-             && local_gamemission <= pack_plut)
+    else if (local_gamemission >= doom2 && local_gamemission <= pack_plut)
     {
         W_AddBaseDir("doom2-all");
     }