diff --git a/src/tag/index.ts b/src/tag/index.ts
index a7325185..e3ab8bb7 100644
--- a/src/tag/index.ts
+++ b/src/tag/index.ts
@@ -12,8 +12,8 @@ export type Tags = {
   count: number
 }[]
 
-export const formatTag = (tag: string) =>
-  capitalizeWords(tag.replaceAll('-', ' '));
+export const formatTag = (tag?: string) =>
+  capitalizeWords(tag?.replaceAll('-', ' '));
 
 export const titleForTag = (
   tag: string,
diff --git a/src/utility/string.ts b/src/utility/string.ts
index 74b3b94f..4f840741 100644
--- a/src/utility/string.ts
+++ b/src/utility/string.ts
@@ -10,7 +10,7 @@ export const convertStringToArray = (
 export const capitalize = (string: string) =>
   string.charAt(0).toUpperCase() + string.slice(1);
 
-export const capitalizeWords = (string: string) =>
+export const capitalizeWords = (string = '') =>
   string
     .split(' ')
     .map(capitalize)