diff --git a/Userland/Libraries/LibWeb/XHR/ProgressEvent.h b/Userland/Libraries/LibWeb/XHR/ProgressEvent.h
index f588c06bfa..c789b2f795 100644
--- a/Userland/Libraries/LibWeb/XHR/ProgressEvent.h
+++ b/Userland/Libraries/LibWeb/XHR/ProgressEvent.h
@@ -8,16 +8,14 @@
 
 #include <AK/FlyString.h>
 #include <LibWeb/DOM/Event.h>
+#include <LibWeb/WebIDL/Types.h>
 
 namespace Web::XHR {
 
-// FIXME: All the "u32"s should be "u64"s, however LibJS doesn't currently support constructing values with u64,
-//        and the IDL parser doesn't properly parse "unsigned long long".
-
 struct ProgressEventInit : public DOM::EventInit {
     bool length_computable { false };
-    u32 loaded { 0 };
-    u32 total { 0 };
+    WebIDL::UnsignedLongLong loaded { 0 };
+    WebIDL::UnsignedLongLong total { 0 };
 };
 
 class ProgressEvent final : public DOM::Event {
diff --git a/Userland/Libraries/LibWeb/XHR/ProgressEvent.idl b/Userland/Libraries/LibWeb/XHR/ProgressEvent.idl
index 169228cd20..f0b796ac65 100644
--- a/Userland/Libraries/LibWeb/XHR/ProgressEvent.idl
+++ b/Userland/Libraries/LibWeb/XHR/ProgressEvent.idl
@@ -12,6 +12,6 @@ interface ProgressEvent : Event {
 
 dictionary ProgressEventInit : EventInit {
     boolean lengthComputable = false;
-    unsigned long loaded = 0;
-    unsigned long total = 0;
+    unsigned long long loaded = 0;
+    unsigned long long total = 0;
 };