diff --git a/MigrationUtility/Scripts/UpdatePhobosTags.sed b/MigrationUtility/Scripts/UpdatePhobosTags.sed
index 12ac756..3d30b10 100644
--- a/MigrationUtility/Scripts/UpdatePhobosTags.sed
+++ b/MigrationUtility/Scripts/UpdatePhobosTags.sed
@@ -32,6 +32,11 @@ s/^LimboKill\.Affected=/LimboKill\.AffectsHouse=/I
 # from post-0.3 devbuilds
 # =============================================
 s/^AnimList\.ShowOnZeroDamage=/CreateAnimsOnZeroDamage=/I
+s/^CustomGS=(y.*|t.*|1)/; &\n; FIXME Enable new FPS system with EnableCustomFPS=true and set target FPS for each speed position using CustomGameSpeedFPS\.0-6 keys\. The old CustomGS system used intervals\/delays which cannot be directly converted\./I
+s/^CustomGS=(n.*|f.*|0)/; &\n; FIXME The old CustomGS system has been replaced\. If you want custom game speeds\, use EnableCustomFPS=true and CustomGameSpeedFPS\.0-6 keys instead\./I
+s/^CustomGS[0-6]\.ChangeInterval=(.*)/; &\n; FIXME Convert to direct FPS using CustomGameSpeedFPS\.N keys\. Old interval-based timing cannot be automatically migrated\./I
+s/^CustomGS[0-6]\.ChangeDelay=(.*)/; &\n; FIXME Convert to direct FPS using CustomGameSpeedFPS\.N keys\. Old delay-based timing cannot be automatically migrated\./I
+s/^CustomGS[0-6]\.DefaultDelay=(.*)/; &\n; FIXME Convert to direct FPS using CustomGameSpeedFPS\.N keys\. Old delay-based timing cannot be automatically migrated\./I
 
 # from pre-0.3
 # =============================================