diff --git a/src/lua_baselib.c b/src/lua_baselib.c
index f2cb803d7..c0b678234 100644
--- a/src/lua_baselib.c
+++ b/src/lua_baselib.c
@@ -2364,7 +2364,7 @@ static int lib_rChar2Frame(lua_State *L)
 {
 	const char *p = luaL_checkstring(L, 1);
 	//HUDSAFE
-	lua_pushinteger(L, R_Char2Frame(*p)); // first character only
+	lua_pushinteger(L, R_Char2Frame(*p, lua_compatmode)); // first character only
 	return 1;
 }
 
@@ -2374,7 +2374,7 @@ static int lib_rFrame2Char(lua_State *L)
 	char c[2] = "";
 	//HUDSAFE
 
-	c[0] = R_Frame2Char(ch);
+	c[0] = R_Frame2Char(ch, lua_compatmode);
 	c[1] = 0;
 
 	lua_pushstring(L, c);
diff --git a/src/lua_infolib.c b/src/lua_infolib.c
index df55de66e..b9815f4f6 100644
--- a/src/lua_infolib.c
+++ b/src/lua_infolib.c
@@ -260,7 +260,7 @@ static UINT8 GetPivotFrame(lua_State *L, int idx)
 	}
 	else
 	{
-		frame = R_Char2Frame(field[0]);
+		frame = R_Char2Frame(field[0], false);
 		if (frame == 255)
 			luaL_error(L, "invalid frame %s", field);
 	}
diff --git a/src/r_picformats.c b/src/r_picformats.c
index 13ffd7495..c382bcbc0 100644
--- a/src/r_picformats.c
+++ b/src/r_picformats.c
@@ -1502,7 +1502,7 @@ static boolean R_ParseSpriteInfoFrame(struct ParseSpriteInfoState *parser, boole
 		else
 			frameChar = sprinfoToken;
 
-		frameFrame = R_Char2Frame(frameChar[0]);
+		frameFrame = R_Char2Frame(frameChar[0], false);
 		Z_Free(sprinfoToken);
 	}
 
diff --git a/src/r_things.cpp b/src/r_things.cpp
index 293c9feee..205eb7ea9 100644
--- a/src/r_things.cpp
+++ b/src/r_things.cpp
@@ -136,7 +136,7 @@ static void R_InstallSpriteLump(UINT16 wad,            // graphics patch
                                 UINT8 rotation,
                                 UINT8 flipped)
 {
-	char cn = R_Frame2Char(frame), cr = R_Rotation2Char(rotation); // for debugging
+	char cn = R_Frame2Char(frame, wadfiles[wad]->compatmode), cr = R_Rotation2Char(rotation); // for debugging
 
 	INT32 r;
 	lumpnum_t lumppat = wad;
@@ -294,6 +294,7 @@ boolean R_AddSingleSpriteDef(const char *sprname, spritedef_t *spritedef, UINT16
 	lumpinfo_t *lumpinfo;
 	softwarepatch_t patch;
 	UINT16 numadded = 0;
+	boolean compat = wadfiles[wadnum]->compatmode;
 
 	memset(sprtemp,0xFF, sizeof (sprtemp));
 	maxframe = (size_t)-1;
@@ -328,7 +329,7 @@ boolean R_AddSingleSpriteDef(const char *sprname, spritedef_t *spritedef, UINT16
 			boolean isPNG = false;
 #endif
 
-			frame = R_Char2Frame(lumpinfo[l].name[4]);
+			frame = R_Char2Frame(lumpinfo[l].name[4], compat);
 			rotation = R_Char2Rotation(lumpinfo[l].name[5]);
 
 			if (frame >= 64 || rotation == 255) // Give an actual NAME error -_-...
@@ -382,7 +383,7 @@ boolean R_AddSingleSpriteDef(const char *sprname, spritedef_t *spritedef, UINT16
 
 			if (lumpinfo[l].name[6])
 			{
-				frame = R_Char2Frame(lumpinfo[l].name[6]);
+				frame = R_Char2Frame(lumpinfo[l].name[6], compat);
 				rotation = R_Char2Rotation(lumpinfo[l].name[7]);
 
 				if (frame >= 64 || rotation == 255) // Give an actual NAME error -_-...
@@ -440,7 +441,7 @@ boolean R_AddSingleSpriteDef(const char *sprname, spritedef_t *spritedef, UINT16
 		{
 			case SRF_NONE:
 			// no rotations were found for that frame at all
-			I_Error("R_AddSingleSpriteDef: No patches found for %.4s frame %c", sprname, R_Frame2Char(frame));
+			I_Error("R_AddSingleSpriteDef: No patches found for %.4s frame %c", sprname, R_Frame2Char(frame, compat));
 			break;
 
 			case SRF_SINGLE:
@@ -451,7 +452,7 @@ boolean R_AddSingleSpriteDef(const char *sprname, spritedef_t *spritedef, UINT16
 			// we test to see whether the left and right slots are present
 			if ((sprtemp[frame].lumppat[2] == LUMPERROR) || (sprtemp[frame].lumppat[6] == LUMPERROR))
 				I_Error("R_AddSingleSpriteDef: Sprite %.4s frame %c is missing rotations (L-R mode)",
-				sprname, R_Frame2Char(frame));
+				sprname, R_Frame2Char(frame, compat));
 			break;
 
 			default:
@@ -462,7 +463,7 @@ boolean R_AddSingleSpriteDef(const char *sprname, spritedef_t *spritedef, UINT16
 				// if it was not loaded the two are LUMPERROR
 				if (sprtemp[frame].lumppat[rotation] == LUMPERROR)
 					I_Error("R_AddSingleSpriteDef: Sprite %.4s frame %c is missing rotations (1-%c mode)",
-					        sprname, R_Frame2Char(frame), ((sprtemp[frame].rotate & SRF_3DGE) ? 'G' : '8'));
+					        sprname, R_Frame2Char(frame, compat), ((sprtemp[frame].rotate & SRF_3DGE) ? 'G' : '8'));
 			break;
 		}
 	}
diff --git a/src/r_things.h b/src/r_things.h
index c51ab69ca..9d87e6528 100644
--- a/src/r_things.h
+++ b/src/r_things.h
@@ -273,33 +273,30 @@ void R_InitDrawNodes(void);
 // as much as possible while also defining all 64 slots in a sane manner
 // 2.1:    [[ ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~   ]]
 // Future: [[ ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789abcdefghijklmnopqrstuvwxyz!@ ]]
-FUNCMATH FUNCINLINE static ATTRINLINE char R_Frame2Char(UINT8 frame)
+FUNCMATH FUNCINLINE static ATTRINLINE char R_Frame2Char(UINT8 frame, boolean compat)
 {
-#if 1 // 2.1 compat
-	return 'A' + frame;
-#else
+	if (compat)
+		return 'A' + frame;
+
 	if (frame < 26) return 'A' + frame;
 	if (frame < 36) return '0' + (frame - 26);
 	if (frame < 62) return 'a' + (frame - 36);
 	if (frame == 62) return '!';
 	if (frame == 63) return '@';
 	return '\xFF';
-#endif
 }
 
-FUNCMATH FUNCINLINE static ATTRINLINE UINT8 R_Char2Frame(char cn)
+FUNCMATH FUNCINLINE static ATTRINLINE UINT8 R_Char2Frame(char cn, boolean compat)
 {
-#if 1 // 2.1 compat
-	if (cn == '+') return '\\' - 'A'; // PK3 can't use backslash, so use + instead
-	return cn - 'A';
-#else
+	if (compat)
+		return (cn == '+' ? '\\' : cn) - 'A'; // PK3 can't use backslash, so use + instead
+
 	if (cn >= 'A' && cn <= 'Z') return (cn - 'A');
 	if (cn >= '0' && cn <= '9') return (cn - '0') + 26;
 	if (cn >= 'a' && cn <= 'z') return (cn - 'a') + 36;
 	if (cn == '!') return 62;
 	if (cn == '@') return 63;
 	return 255;
-#endif
 }
 
 // "Left" and "Right" character symbols for additional rotation functionality