diff --git a/lib/entry-points.js b/lib/entry-points.js
index aefa923c0..083567dfb 100644
--- a/lib/entry-points.js
+++ b/lib/entry-points.js
@@ -144556,14 +144556,14 @@ function checkSchema(schema, obj, options = {}, path29 = "") {
     if (validator.required && !hasKey) {
       result.valid = false;
       if (options.failFast) {
-        return result;
+        break;
       }
       continue;
     }
     if (validator.required && (obj[key] === void 0 || obj[key] === null)) {
       result.valid = false;
       if (options.failFast) {
-        return result;
+        break;
       }
       continue;
     }
@@ -144577,7 +144577,7 @@ function checkSchema(schema, obj, options = {}, path29 = "") {
       if (!checkResult.valid) {
         result.valid = false;
         if (options.failFast) {
-          return result;
+          break;
         }
         continue;
       }
diff --git a/src/json/index.ts b/src/json/index.ts
index 2d50ff121..78923f8ba 100644
--- a/src/json/index.ts
+++ b/src/json/index.ts
@@ -264,9 +264,16 @@ export function checkSchema<S extends Schema>(
   path: string = "",
 ): CheckSchemaResult {
   const result: CheckSchemaResult = successfulCheckSchema();
+
+  // Track the set of input keys. We remove keys from this set as we recognise them
+  // during validation.
   const inputKeys = new Set(Object.keys(obj));
+
+  // Track keys that have failed validation, starting with the empty set.
   const invalidKeys = new Set();
 
+  // Loop through all keys in the object schema and validate that the given object
+  // satisfies the schema key.
   for (const [key, validator] of Object.entries(schema)) {
     const hasKey = key in obj;
 
@@ -282,7 +289,7 @@ export function checkSchema<S extends Schema>(
       result.valid = false;
 
       if (options.failFast) {
-        return result;
+        break;
       }
       continue;
     }
@@ -292,7 +299,7 @@ export function checkSchema<S extends Schema>(
       result.valid = false;
 
       if (options.failFast) {
-        return result;
+        break;
       }
       continue;
     }
@@ -314,7 +321,7 @@ export function checkSchema<S extends Schema>(
         result.valid = false;
 
         if (options.failFast) {
-          return result;
+          break;
         }
         continue;
       }