diff --git a/src/app/core/models/course.ts b/src/app/core/models/course.ts
index d96769e1d8a6132a5ee32a5a11973d7d043e4482..e21b08d41dc853a9a9c0810a84ce4a53f38a018e 100644
--- a/src/app/core/models/course.ts
+++ b/src/app/core/models/course.ts
@@ -10,7 +10,7 @@ export interface CourseBase {
   creditMin: number;
   creditMax: number;
   grade?: any;
-  classNumber: string;
+  classNumber: string | null;
   courseOrder: number;
   honors: string;
   waitlist: string;
diff --git a/src/app/degree-planner/store/reducer.ts b/src/app/degree-planner/store/reducer.ts
index b7ca18ed5300244803b468f37c0e8ba503c4719c..74b2686bf1a82f0cba5ebc57f876d9593ba82c92 100644
--- a/src/app/degree-planner/store/reducer.ts
+++ b/src/app/degree-planner/store/reducer.ts
@@ -346,8 +346,9 @@ export function degreePlannerReducer(
       const { yearCode: fromYearCode } = fromTermCode;
       const { yearCode: toYearCode } = toTermCode;
       const course = findCourse(state.visibleYears, fromTermCode, id);
-      this.course.classNumber = null;
+
       if (course && course.id !== null) {
+        course.classNumber = null;
         const fromYear = createYearWithoutCourse(
           fromTermCode,
           course.id,