diff --git a/backend/nestjs-seshat-api/src/library/library.controller.ts b/backend/nestjs-seshat-api/src/library/library.controller.ts
index 177e998..bd5a067 100644
--- a/backend/nestjs-seshat-api/src/library/library.controller.ts
+++ b/backend/nestjs-seshat-api/src/library/library.controller.ts
@@ -82,6 +82,19 @@ export class LibraryController {
     @Res({ passthrough: true }) response: Response,
   ) {
     try {
+      const series = await this.series.getSeries({
+        provider: body.provider,
+        providerSeriesId: body.providerSeriesId,
+      });
+
+      if (!series) {
+        response.statusCode = 404;
+        return {
+          success: false,
+          error_message: 'Series has not been added.'
+        };
+      }
+
       await this.library.updateSeries({
         provider: body.provider,
         providerSeriesId: body.providerSeriesId,
@@ -93,17 +106,6 @@ export class LibraryController {
         success: true,
       };
     } catch (err) {
-      if (err instanceof QueryFailedError) {
-        if (err.driverError.code == '23505') {
-          // Subscription already exist.
-          response.statusCode = 409;
-          return {
-            success: false,
-            error_message: 'Series subscription already exists.',
-          };
-        }
-      }
-
       response.statusCode = 500;
       return {
         success: false,
@@ -149,7 +151,7 @@ export class LibraryController {
           };
         } else if (err.driverError.code == '23503') {
           // Series does not exist.
-          response.statusCode = 400;
+          response.statusCode = 404;
           return {
             success: false,
             error_message: 'Series does not exist.',