diff --git a/src/g_level.cpp b/src/g_level.cpp
index d161059e6..c21031706 100644
--- a/src/g_level.cpp
+++ b/src/g_level.cpp
@@ -151,9 +151,9 @@ CUSTOM_CVAR(Int, gl_maplightmode, -1, CVAR_NOINITCALL) // this is just for testi
 	if (self > 5 || self < -1) self = -1;
 }
 
-CUSTOM_CVAR(Int, gl_lightmode, 1, CVAR_ARCHIVE | CVAR_NOINITCALL)
+CUSTOM_CVAR(Int, gl_lightmode, 1, CVAR_ARCHIVE)
 {
-	if (self < 0 || self > 2) self = 2;
+	if (self < 0 || self > 2) self = 1;
 }
 
 ELightMode getRealLightmode(FLevelLocals* Level, bool for3d)
diff --git a/src/gameconfigfile.cpp b/src/gameconfigfile.cpp
index 5a801bff3..0b3931e88 100644
--- a/src/gameconfigfile.cpp
+++ b/src/gameconfigfile.cpp
@@ -612,7 +612,7 @@ void FGameConfigFile::DoGlobalSetup ()
 				if (const auto var = FindCVar("gl_lightmode", NULL))
 				{
 					UCVarValue v = var->GetGenericRep(CVAR_Int);
-					v.Int /= 8; // all legacy modes map to 0, ZDoom software to 1 and Vanilla software to 2.
+					v.Int = v.Int == 16 ? 2 : v.Int == 8 ? 1 : 0;
 					var->SetGenericRep(v, CVAR_Int);
 				}
 			}