diff --git a/docs/rh-log.txt b/docs/rh-log.txt
index a96587d97..2823d3c21 100644
--- a/docs/rh-log.txt
+++ b/docs/rh-log.txt
@@ -1,4 +1,6 @@
 March 23, 2008 (Changes by Graf Zahl)
+- Fixed: The sector translators must clear unused bits because they might
+  render a sector's special inoperable.
 - Expanded the args for MAPINFO special actions to 32 bit integers as in
   the rest of the game.
 - Fixed: The specialaction list was not copied properly when transferred
diff --git a/src/p_xlat.cpp b/src/p_xlat.cpp
index 9fae187b1..7eafaa067 100644
--- a/src/p_xlat.cpp
+++ b/src/p_xlat.cpp
@@ -330,13 +330,6 @@ int P_TranslateSectorSpecial (int special)
 {
 	int mask = 0;
 
-	// Allow any supported sector special by or-ing 0x8000 to it in Doom format maps
-	// That's for those who like to mess around with existing maps. ;)
-	if (special & 0x8000)
-	{
-		return special & 0x7fff;
-	}
-
 	for(unsigned i = 0; i < SectorMasks.Size(); i++)
 	{
 		int newmask = special & SectorMasks[i].mask;
@@ -345,6 +338,7 @@ int P_TranslateSectorSpecial (int special)
 			special &= ~newmask;
 			if (SectorMasks[i].op == 1) newmask <<= SectorMasks[i].shift;
 			else if (SectorMasks[i].op == -1) newmask >>= SectorMasks[i].shift;
+			else if (SectorMasks[i].op == 0 && SectorMasks[i].shift ==1) newmask = 0;
 			mask |= newmask;
 		}
 	}
diff --git a/src/xlat/parse_xlat.cpp b/src/xlat/parse_xlat.cpp
index d414ccb41..a5472f887 100644
--- a/src/xlat/parse_xlat.cpp
+++ b/src/xlat/parse_xlat.cpp
@@ -161,14 +161,14 @@ struct XlatParseContext
 		{
 			"include", "define", "enum",
 			"arg5", "arg4", "arg3", "arg2", "flags", "lineid", "tag",
-			"sector", "bitmask", "nobitmask"
+			"sector", "bitmask", "nobitmask", "clear"
 			
 		};
 		static const short types[] =
 		{
 			INCLUDE, DEFINE, ENUM,
 			ARG5, ARG4, ARG3, ARG2, FLAGS, TAG, TAG,
-			SECTOR, BITMASK, NOBITMASK
+			SECTOR, BITMASK, NOBITMASK, CLEAR
 		};
 		int i;
 
diff --git a/src/xlat/xlat_parser.h b/src/xlat/xlat_parser.h
index 3fa54abce..4a1bb3a40 100644
--- a/src/xlat/xlat_parser.h
+++ b/src/xlat/xlat_parser.h
@@ -32,5 +32,6 @@
 #define SEMICOLON                      32
 #define NOBITMASK                      33
 #define BITMASK                        34
-#define LSHASSIGN                      35
-#define RSHASSIGN                      36
+#define CLEAR                          35
+#define LSHASSIGN                      36
+#define RSHASSIGN                      37
diff --git a/src/xlat/xlat_parser.y b/src/xlat/xlat_parser.y
index b3b9f9482..4974f7f2d 100644
--- a/src/xlat/xlat_parser.y
+++ b/src/xlat/xlat_parser.y
@@ -488,6 +488,12 @@ sector_bitmask ::= SECTOR BITMASK exp(mask) SEMICOLON.
 	SectorMasks.Push(sm);
 }
 
+sector_bitmask ::= SECTOR BITMASK exp(mask) CLEAR SEMICOLON.
+{
+	FSectorMask sm = { mask, 0, 1};
+	SectorMasks.Push(sm);
+}
+
 sector_op(A) ::= LSHASSIGN.		{ A = 1; }
 sector_op(A) ::= RSHASSIGN.		{ A = -1; }
 
diff --git a/wadsrc/xlat/doom.txt b/wadsrc/xlat/doom.txt
index c07c9e3ab..25b84b2f0 100644
--- a/wadsrc/xlat/doom.txt
+++ b/wadsrc/xlat/doom.txt
@@ -1,6 +1,7 @@
 include "xlat/base.txt"
 
 
+sector bitmask 0xf000 clear;
 sector bitmask 0xfe0 <<= 3;
 
 sector 1 = dLight_Flicker;
diff --git a/wadsrc/xlat/heretic.txt b/wadsrc/xlat/heretic.txt
index 0632a9ae5..b1a4908b0 100644
--- a/wadsrc/xlat/heretic.txt
+++ b/wadsrc/xlat/heretic.txt
@@ -10,6 +10,7 @@ include "xlat/base.txt"
 106 = WALK,				Stairs_BuildUpDoom (tag, F_SLOW, 16)
 107 = USE,				Stairs_BuildUpDoom (tag, F_SLOW, 16)
 
+sector bitmask 0xf000 clear;
 sector bitmask 0xfc0 <<= 3;
 
 sector 1 = dLight_Flicker;
diff --git a/wadsrc/xlat/strife.txt b/wadsrc/xlat/strife.txt
index bd9e9056a..72ae2686b 100644
--- a/wadsrc/xlat/strife.txt
+++ b/wadsrc/xlat/strife.txt
@@ -324,6 +324,7 @@ RetailOnly		= 121
 233 = USE|REP,		ACS_ExecuteWithResult (0, 233, tag)
 234 = USE|REP,		ACS_ExecuteWithResult (0, 234, tag)
 
+sector bitmask 0xf000 clear;
 sector bitmask 0xfe0 <<= 3;
 
 sector 1 = dLight_Flicker;