diff --git a/src/m_cond.c b/src/m_cond.c
index 40d38e7c8..6ddbed1f9 100644
--- a/src/m_cond.c
+++ b/src/m_cond.c
@@ -1838,7 +1838,7 @@ boolean M_CupLocked(cupheader_t *cup)
 	return false;
 }
 
-boolean M_MapLocked(INT32 mapnum)
+boolean M_MapLocked(UINT16 mapnum)
 {
 	UINT8 i;
 
@@ -1851,7 +1851,7 @@ boolean M_MapLocked(INT32 mapnum)
 	if (marathonmode)
 		return false;
 
-	if (!mapnum || mapnum > nummapheaders)
+	if (mapnum <= 1 || mapnum > nummapheaders)
 		return false;
 	
 	if (!mapheaderinfo[mapnum-1])
diff --git a/src/m_cond.h b/src/m_cond.h
index 3dafef72f..a8c66c98e 100644
--- a/src/m_cond.h
+++ b/src/m_cond.h
@@ -341,7 +341,7 @@ UINT8 M_CompletionEmblems(void);
 boolean M_CheckNetUnlockByID(UINT8 unlockid);
 boolean M_SecretUnlocked(INT32 type, boolean local);
 boolean M_CupLocked(cupheader_t *cup);
-boolean M_MapLocked(INT32 mapnum);
+boolean M_MapLocked(UINT16 mapnum);
 INT32 M_CountMedals(boolean all, boolean extraonly);
 
 // Emblem shit
diff --git a/src/menus/transient/level-select.c b/src/menus/transient/level-select.c
index a8f4203af..19f7ca18e 100644
--- a/src/menus/transient/level-select.c
+++ b/src/menus/transient/level-select.c
@@ -58,7 +58,7 @@ boolean M_CanShowLevelInList(INT16 mapnum, levelsearch_t *levelsearch)
 		return false;
 
 	// Check for TOL
-	if (!(mapheaderinfo[mapnum]->typeoflevel & levelsearch->typeoflevel))
+	if (mapheaderinfo[mapnum]->typeoflevel && !(mapheaderinfo[mapnum]->typeoflevel & levelsearch->typeoflevel))
 		return false;
 
 	// Should the map be hidden?