diff --git a/src/lua_maplib.c b/src/lua_maplib.c
index c946b10ce220fd28e2415d46f68233fad4bc7f0b..2740c957f4f89e4c9616f32ee3dc8ca437895033 100644
--- a/src/lua_maplib.c
+++ b/src/lua_maplib.c
@@ -2695,7 +2695,7 @@ static int slope_set(lua_State *L)
 		if (zangle == ANGLE_90 || zangle == ANGLE_270)
 			return luaL_error(L, "invalid zangle for slope!");
 		slope->zangle = zangle;
-		slope->zdelta = -FINETANGENT(((slope->zangle+ANGLE_90)>>ANGLETOFINESHIFT) & 4095);
+		slope->zdelta = -FINETANGENT(((slope->zangle+ANGLE_90)>>ANGLETOFINESHIFT) & TANMASK);
 		slope->dzdelta = FixedToDouble(slope->zdelta);
 		P_CalculateSlopeNormal(slope);
 		break;
diff --git a/src/lua_mathlib.c b/src/lua_mathlib.c
index 1bc6019dee9a507ebc6350a541807e75e53726d7..4dcee68c83997a5231739af2dad481f3add88110 100644
--- a/src/lua_mathlib.c
+++ b/src/lua_mathlib.c
@@ -83,8 +83,8 @@ static int lib_finecosine(lua_State *L)
 static int lib_finetangent(lua_State *L)
 {
 	// HACK: add ANGLE_90 to make tan() in Lua start at 0 like it should
-	// use & 4095 instead of & FINEMASK (8191), so it doesn't go out of the array's bounds
-	lua_pushfixed(L, FINETANGENT(((luaL_checkangle(L, 1)+ANGLE_90)>>ANGLETOFINESHIFT) & 4095));
+	// use & TANMASK (4095) instead of & FINEMASK (8191), so it doesn't go out of the array's bounds
+	lua_pushfixed(L, FINETANGENT(((luaL_checkangle(L, 1)+ANGLE_90)>>ANGLETOFINESHIFT) & TANMASK));
 	return 1;
 }
 
diff --git a/src/r_segs.c b/src/r_segs.c
index 510744ebce3853e36a09d8bc247c73e721329d97..bee349492e5b827f06820301e90cf5c6c3149585 100644
--- a/src/r_segs.c
+++ b/src/r_segs.c
@@ -1463,7 +1463,7 @@ static void R_RenderSegLoop (void)
 		//SoM: Calculate offsets for Thick fake floors.
 		// calculate texture offset
 		angle = (rw_centerangle + xtoviewangle[rw_x])>>ANGLETOFINESHIFT;
-		textureoffset = rw_offset - FixedMul(FINETANGENT(angle), rw_distance);
+		textureoffset = rw_offset - FixedMul(FINETANGENT(angle & TANMASK), rw_distance);
 		texturecolumn = FixedDiv(textureoffset, rw_invmidtexturescalex);
 
 		// texturecolumn and lighting are independent of wall tiers
diff --git a/src/tables.h b/src/tables.h
index 3c0dd2a81ff97a6ccc382716bf136a897b1c4e75..43817e25d3ed6ab78e695e8c8512fb6cb1ea61d7 100644
--- a/src/tables.h
+++ b/src/tables.h
@@ -22,6 +22,7 @@
 
 #define FINEANGLES 8192
 #define FINEMASK (FINEANGLES - 1)
+#define TANMASK 4095
 #define ANGLETOFINESHIFT 19 // 0x100000000 to 0x2000
 #define FINEANGLE_C(x) ((FixedAngle((x)*FRACUNIT)>>ANGLETOFINESHIFT) & FINEMASK) // ((x*(ANGLE_45/45))>>ANGLETOFINESHIFT) & FINEMASK