diff --git a/api/src/services/import-services/critter/critter-header-configs.test.ts b/api/src/services/import-services/critter/critter-header-configs.test.ts
index c58549befe..d965a70a2f 100644
--- a/api/src/services/import-services/critter/critter-header-configs.test.ts
+++ b/api/src/services/import-services/critter/critter-header-configs.test.ts
@@ -197,7 +197,7 @@ describe('critter-header-configs', () => {
         new CSVConfigUtils(xlsx.utils.json_to_sheet([]), mockConfig)
       );
 
-      const cellValues = ['male', 'MALE'];
+      const cellValues = ['male', 'MALE', undefined];
 
       for (const cell of cellValues) {
         const result = cellValidator({ cell: cell, row: { ITIS_TSN: 1 }, header: 'HEADER', rowIndex: 0 });
@@ -216,7 +216,7 @@ describe('critter-header-configs', () => {
         new CSVConfigUtils(xlsx.utils.json_to_sheet([]), mockConfig)
       );
 
-      const cellValues = [undefined, '', 0];
+      const cellValues = ['', 0];
 
       for (const cell of cellValues) {
         const result = cellValidator({ cell: cell, row: { ITIS_TSN: 1 }, header: 'HEADER', rowIndex: 0 });
diff --git a/api/src/services/import-services/critter/import-critters-services.test.ts b/api/src/services/import-services/critter/import-critters-service.test.ts
similarity index 100%
rename from api/src/services/import-services/critter/import-critters-services.test.ts
rename to api/src/services/import-services/critter/import-critters-service.test.ts
diff --git a/api/src/services/import-services/critter/import-critters-service.ts b/api/src/services/import-services/critter/import-critters-service.ts
index 8a054d0b87..c714f56530 100644
--- a/api/src/services/import-services/critter/import-critters-service.ts
+++ b/api/src/services/import-services/critter/import-critters-service.ts
@@ -60,7 +60,7 @@ export class ImportCrittersService extends DBService {
       staticHeadersConfig: {
         ITIS_TSN: { aliases: ['TAXON', 'SPECIES', 'TSN'] },
         ALIAS: { aliases: ['NICKNAME', 'NAME', 'ANIMAL_ID'] },
-        SEX: { aliases: [] },
+        SEX: { aliases: [], optional: true },
         WLH_ID: { aliases: ['WILDLIFE_HEALTH_ID', 'WILD LIFE HEALTH ID', 'WLHID'], optional: true },
         DESCRIPTION: { aliases: ['COMMENTS', 'COMMENT', 'NOTES'], optional: true }
       },
diff --git a/api/src/utils/csv-utils/csv-config-validation.test.ts b/api/src/utils/csv-utils/csv-config-validation.test.ts
index 3e77d7c112..71b63aae1e 100644
--- a/api/src/utils/csv-utils/csv-config-validation.test.ts
+++ b/api/src/utils/csv-utils/csv-config-validation.test.ts
@@ -159,6 +159,18 @@ describe('csv-config-validation', () => {
       ]);
     });
 
+    it('should NOT return an error if the worksheet is missing a optional header', () => {
+      const mockConfig: CSVConfig = {
+        staticHeadersConfig: { ALIAS: { aliases: [], optional: true } },
+        ignoreDynamicHeaders: true
+      };
+      const worksheet: WorkSheet = xlsx.utils.json_to_sheet([{ NOT_ALIAS: 'value' }]);
+
+      const result = validateCSVHeaders(worksheet, mockConfig);
+
+      expect(result).to.deep.equal([]);
+    });
+
     it('should return an error if the worksheet has an unknown header and dynamic headers are not ignored', () => {
       const mockConfig: CSVConfig = { staticHeadersConfig: { ALIAS: { aliases: [] } }, ignoreDynamicHeaders: false };
       const worksheet: WorkSheet = xlsx.utils.json_to_sheet([{ ALIAS: 'alias', UNKNOWN_HEADER: 'value' }]);