diff --git a/src/taglist.c b/src/taglist.c
index 5174fe2d7..bfa5814dd 100644
--- a/src/taglist.c
+++ b/src/taglist.c
@@ -2,7 +2,7 @@
 #include "z_zone.h"
 #include "r_data.h"
 
-void Tag_Add (taglist_t* list, const UINT16 tag)
+void Tag_Add (taglist_t* list, const mtag_t tag)
 {
 	list->tags = Z_Realloc(list->tags, (list->count + 1) * sizeof(list->tags), PU_LEVEL, NULL);
 	list->tags[list->count++] = tag;
@@ -22,121 +22,121 @@ boolean Tag_Compare (const taglist_t* list1, const taglist_t* list2)
 	return true;
 }
 
-void Taglist_AddToSectors (const size_t tag, const size_t itemid)
+void Taglist_AddToSectors (const mtag_t tag, const size_t itemid)
 {
 	taggroup_t* tagelems;
 
-	if (tag == -1)
+	if (tag == MTAG_GLOBAL)
 		return;
 
-	if (!tags_sectors[tag])
-		tags_sectors[tag] = Z_Calloc(sizeof(taggroup_t), PU_LEVEL, NULL);
+	if (!tags_sectors[(UINT16)tag])
+		tags_sectors[(UINT16)tag] = Z_Calloc(sizeof(taggroup_t), PU_LEVEL, NULL);
 
-	tagelems = tags_sectors[tag];
+	tagelems = tags_sectors[(UINT16)tag];
 	tagelems->count++;
 	tagelems->elements = Z_Realloc(tagelems->elements, tagelems->count * sizeof(size_t), PU_LEVEL, NULL);
 	tagelems->elements[tagelems->count - 1] = itemid;
 }
 
-void Taglist_AddToLines (const size_t tag, const size_t itemid)
+void Taglist_AddToLines (const mtag_t tag, const size_t itemid)
 {
 	taggroup_t* tagelems;
 
-	if (tag == -1)
+	if (tag == MTAG_GLOBAL)
 		return;
 
-	if (!tags_lines[tag])
-		tags_lines[tag] = Z_Calloc(sizeof(taggroup_t), PU_LEVEL, NULL);
+	if (!tags_lines[(UINT16)tag])
+		tags_lines[(UINT16)tag] = Z_Calloc(sizeof(taggroup_t), PU_LEVEL, NULL);
 
-	tagelems = tags_lines[tag];
+	tagelems = tags_lines[(UINT16)tag];
 	tagelems->count++;
 	tagelems->elements = Z_Realloc(tagelems->elements, tagelems->count * sizeof(size_t), PU_LEVEL, NULL);
 	tagelems->elements[tagelems->count - 1] = itemid;
 }
 
-void Taglist_AddToMapthings (const size_t tag, const size_t itemid)
+void Taglist_AddToMapthings (const mtag_t tag, const size_t itemid)
 {
 	taggroup_t* tagelems;
 
-	if (tag == -1)
+	if (tag == MTAG_GLOBAL)
 		return;
 
-	if (!tags_mapthings[tag])
-		tags_mapthings[tag] = Z_Calloc(sizeof(taggroup_t), PU_LEVEL, NULL);
+	if (!tags_mapthings[(UINT16)tag])
+		tags_mapthings[(UINT16)tag] = Z_Calloc(sizeof(taggroup_t), PU_LEVEL, NULL);
 
-	tagelems = tags_mapthings[tag];
+	tagelems = tags_mapthings[(UINT16)tag];
 	tagelems->count++;
 	tagelems->elements = Z_Realloc(tagelems->elements, tagelems->count * sizeof(size_t), PU_LEVEL, NULL);
 	tagelems->elements[tagelems->count - 1] = itemid;
 }
 
-INT32 Tag_Iterate_Sectors (const INT16 tag, const size_t p)
+INT32 Tag_Iterate_Sectors (const mtag_t tag, const size_t p)
 {
-	if (tag == -1)
+	if (tag == MTAG_GLOBAL)
 	{
 		if (p < numsectors)
 			return p;
 		return -1;
 	}
 
-	if (tags_sectors[tag])
+	if (tags_sectors[(UINT16)tag])
 	{
-		if (p < tags_sectors[tag]->count)
-			return tags_sectors[tag]->elements[p];
+		if (p < tags_sectors[(UINT16)tag]->count)
+			return tags_sectors[(UINT16)tag]->elements[p];
 		return -1;
 	}
 	return -1;
 }
 
-INT32 Tag_Iterate_Lines (const INT16 tag, const size_t p)
+INT32 Tag_Iterate_Lines (const mtag_t tag, const size_t p)
 {
-	if (tag == -1)
+	if (tag == MTAG_GLOBAL)
 	{
 		if (p < numlines)
 			return p;
 		return -1;
 	}
 
-	if (tags_lines[tag])
+	if (tags_lines[(UINT16)tag])
 	{
-		if (p < tags_lines[tag]->count)
-			return tags_lines[tag]->elements[p];
+		if (p < tags_lines[(UINT16)tag]->count)
+			return tags_lines[(UINT16)tag]->elements[p];
 		return -1;
 	}
 	return -1;
 }
 
-INT32 Tag_Iterate_Things (const INT16 tag, const size_t p)
+INT32 Tag_Iterate_Things (const mtag_t tag, const size_t p)
 {
-	if (tag == -1)
+	if (tag == MTAG_GLOBAL)
 	{
 		if (p < nummapthings)
 			return p;
 		return -1;
 	}
 
-	if (tags_mapthings[tag])
+	if (tags_mapthings[(UINT16)tag])
 	{
-		if (p < tags_mapthings[tag]->count)
-			return tags_mapthings[tag]->elements[p];
+		if (p < tags_mapthings[(UINT16)tag]->count)
+			return tags_mapthings[(UINT16)tag]->elements[p];
 		return -1;
 	}
 	return -1;
 }
 
-INT32 Tag_FindLineSpecial(const INT16 special, const INT16 tag)
+INT32 Tag_FindLineSpecial(const INT16 special, const mtag_t tag)
 {
 	INT32 i;
 
-	if (tag == -1)
+	if (tag == MTAG_GLOBAL)
 	{
 		for (i = 0; i < numlines; i++)
 			if (lines[i].special == special)
 				return i;
 	}
-	else if (tags_lines[tag])
+	else if (tags_lines[(UINT16)tag])
 	{
-		taggroup_t *tagged = tags_lines[tag];
+		taggroup_t *tagged = tags_lines[(UINT16)tag];
 		for (i = 0; i < tagged->count; i++)
 			if (lines[tagged->elements[i]].special == special)
 				return tagged->elements[i];
diff --git a/src/taglist.h b/src/taglist.h
index 59ecd6106..67665434c 100644
--- a/src/taglist.h
+++ b/src/taglist.h
@@ -3,14 +3,18 @@
 
 #include "doomtype.h"
 
+typedef INT16 mtag_t;
+#define MAXTAGS UINT16_MAX
+#define MTAG_GLOBAL -1
+
 /// Multitag list.
 typedef struct
 {
-	UINT16* tags;
+	mtag_t* tags;
 	UINT16 count;
 } taglist_t;
 
-void Tag_Add (taglist_t* list, const UINT16 tag);
+void Tag_Add (taglist_t* list, const mtag_t tag);
 boolean Tag_Compare (const taglist_t* list1, const taglist_t* list2);
 
 typedef struct
@@ -19,18 +23,17 @@ typedef struct
 	size_t count;
 } taggroup_t;
 
-#define MAXTAGS 65536
-taggroup_t* tags_sectors[MAXTAGS];
-taggroup_t* tags_lines[MAXTAGS];
-taggroup_t* tags_mapthings[MAXTAGS];
+taggroup_t* tags_sectors[MAXTAGS + 1];
+taggroup_t* tags_lines[MAXTAGS + 1];
+taggroup_t* tags_mapthings[MAXTAGS + 1];
 
-void Taglist_AddToSectors (const size_t tag, const size_t itemid);
-void Taglist_AddToLines (const size_t tag, const size_t itemid);
-void Taglist_AddToMapthings (const size_t tag, const size_t itemid);
+void Taglist_AddToSectors (const mtag_t tag, const size_t itemid);
+void Taglist_AddToLines (const mtag_t tag, const size_t itemid);
+void Taglist_AddToMapthings (const mtag_t tag, const size_t itemid);
 
-INT32 Tag_Iterate_Sectors (const INT16 tag, const size_t p);
-INT32 Tag_Iterate_Lines (const INT16 tag, const size_t p);
-INT32 Tag_Iterate_Things (const INT16 tag, const size_t p);
+INT32 Tag_Iterate_Sectors (const mtag_t tag, const size_t p);
+INT32 Tag_Iterate_Lines (const mtag_t tag, const size_t p);
+INT32 Tag_Iterate_Things (const mtag_t tag, const size_t p);
 
 INT32 Tag_FindLineSpecial(const INT16 special, const INT16 tag);