diff --git a/common/src/config/config.ts b/common/src/config/config.ts
index 5e3439c4b..74727553d 100644
--- a/common/src/config/config.ts
+++ b/common/src/config/config.ts
@@ -65,7 +65,7 @@ interface BaseGamePTConfig<I extends IDStrings> {
 	grades: Grades[I][];
 	gradeColours: Record<Grades[I], string>;
 	clearGrade: Grades[I];
-	gradeBoundaries: number[] |;
+	gradeBoundaries: number[] | null;
 
 	lamps: Lamps[I][];
 	lampColours: Record<Lamps[I], string>;