diff --git a/src/common/getters.ts b/src/common/getters.ts
index 7c9d84d1..416b78d7 100644
--- a/src/common/getters.ts
+++ b/src/common/getters.ts
@@ -465,7 +465,7 @@ function deserializeFields<T>(
       if (result === undefined) {
         // FIXME use inrupt error library
         throw new Error(
-          `Error deserializing value ${object} for predicate ${field.href} as type ${type}.`,
+          `Failed to deserialize value ${object.value} for predicate ${field.href} as type ${type}.`,
         );
       }
       return result;
diff --git a/src/type/CustomField.ts b/src/type/CustomField.ts
index 058e95f8..970e1e6f 100644
--- a/src/type/CustomField.ts
+++ b/src/type/CustomField.ts
@@ -71,7 +71,7 @@ export const toJson = (
         if (!["string", "number", "boolean"].includes(typeof field.value)) {
           // FIXME use inrupt error library
           throw new Error(
-            `All custom fields values must be literals, found ${field.value} (or type ${typeof field.value})`,
+            `All custom fields values must be literals, found ${JSON.stringify(field.value)} (of type ${typeof field.value})`,
           );
         }
         return { [`${field.key.toString()}`]: field.value };