diff --git a/AK/JsonParser.cpp b/AK/JsonParser.cpp
index 3beda694dd9..4d497cb1b50 100644
--- a/AK/JsonParser.cpp
+++ b/AK/JsonParser.cpp
@@ -263,9 +263,13 @@ Optional<JsonValue> JsonParser::parse_number()
         value = JsonValue((double)whole + ((double)fraction / divider));
     } else {
 #endif
-        auto to_unsigned_result = number_string.to_uint();
+        auto to_unsigned_result = number_string.to_uint<u64>();
         if (to_unsigned_result.has_value()) {
-            value = JsonValue(to_unsigned_result.value());
+            auto number = *to_unsigned_result;
+            if (number <= NumericLimits<u32>::max())
+                value = JsonValue((u32)number);
+            else
+                value = JsonValue(number);
         } else {
             auto number = number_string.to_int<i64>();
             if (!number.has_value())
diff --git a/Tests/AK/TestJSON.cpp b/Tests/AK/TestJSON.cpp
index 15f4e9ecade..86d4dce2cee 100644
--- a/Tests/AK/TestJSON.cpp
+++ b/Tests/AK/TestJSON.cpp
@@ -105,3 +105,12 @@ TEST_CASE(json_duplicate_keys)
     json.set("test", "baz");
     EXPECT_EQ(json.to_string(), "{\"test\":\"baz\"}");
 }
+
+TEST_CASE(json_u64_roundtrip)
+{
+    auto big_value = 0xffffffffffffffffull;
+    auto json = JsonValue(big_value).to_string();
+    auto value = JsonValue::from_string(json);
+    EXPECT_EQ_FORCE(value.has_value(), true);
+    EXPECT_EQ(value->as_u64(), big_value);
+}