diff --git a/AK/Function.h b/AK/Function.h
index 5c9f690c91..76777e416b 100644
--- a/AK/Function.h
+++ b/AK/Function.h
@@ -38,10 +38,16 @@ namespace AK {
 
 namespace Detail {
 
-template<typename T, typename... Args>
+template<typename T, typename Out, typename... Args>
 inline constexpr bool IsCallableWithArguments = requires(T t) {
-                                                    t(declval<Args>()...);
-                                                };
+                                                    {
+                                                        t(declval<Args>()...)
+                                                        } -> ConvertibleTo<Out>;
+                                                } || requires(T t) {
+                                                         {
+                                                             t(declval<Args>()...)
+                                                             } -> SameAs<Out>;
+                                                     };
 }
 
 using Detail::IsCallableWithArguments;
@@ -75,14 +81,14 @@ public:
 
     template<typename CallableType>
     Function(CallableType&& callable)
-    requires((IsFunctionObject<CallableType> && IsCallableWithArguments<CallableType, In...> && !IsSame<RemoveCVReference<CallableType>, Function>))
+    requires((IsFunctionObject<CallableType> && IsCallableWithArguments<CallableType, Out, In...> && !IsSame<RemoveCVReference<CallableType>, Function>))
     {
         init_with_callable(forward<CallableType>(callable));
     }
 
     template<typename FunctionType>
     Function(FunctionType f)
-    requires((IsFunctionPointer<FunctionType> && IsCallableWithArguments<RemovePointer<FunctionType>, In...> && !IsSame<RemoveCVReference<FunctionType>, Function>))
+    requires((IsFunctionPointer<FunctionType> && IsCallableWithArguments<RemovePointer<FunctionType>, Out, In...> && !IsSame<RemoveCVReference<FunctionType>, Function>))
     {
         init_with_callable(move(f));
     }
@@ -109,7 +115,7 @@ public:
 
     template<typename CallableType>
     Function& operator=(CallableType&& callable)
-    requires((IsFunctionObject<CallableType> && IsCallableWithArguments<CallableType, In...>))
+    requires((IsFunctionObject<CallableType> && IsCallableWithArguments<CallableType, Out, In...>))
     {
         clear();
         init_with_callable(forward<CallableType>(callable));
@@ -118,7 +124,7 @@ public:
 
     template<typename FunctionType>
     Function& operator=(FunctionType f)
-    requires((IsFunctionPointer<FunctionType> && IsCallableWithArguments<RemovePointer<FunctionType>, In...>))
+    requires((IsFunctionPointer<FunctionType> && IsCallableWithArguments<RemovePointer<FunctionType>, Out, In...>))
     {
         clear();
         if (f)
diff --git a/Userland/Libraries/LibJS/SafeFunction.h b/Userland/Libraries/LibJS/SafeFunction.h
index 7a86dc95c9..0db4df7dd4 100644
--- a/Userland/Libraries/LibJS/SafeFunction.h
+++ b/Userland/Libraries/LibJS/SafeFunction.h
@@ -51,14 +51,14 @@ public:
 
     template<typename CallableType>
     SafeFunction(CallableType&& callable)
-    requires((AK::IsFunctionObject<CallableType> && IsCallableWithArguments<CallableType, In...> && !IsSame<RemoveCVReference<CallableType>, SafeFunction>))
+    requires((AK::IsFunctionObject<CallableType> && IsCallableWithArguments<CallableType, Out, In...> && !IsSame<RemoveCVReference<CallableType>, SafeFunction>))
     {
         init_with_callable(forward<CallableType>(callable), CallableKind::FunctionObject);
     }
 
     template<typename FunctionType>
     SafeFunction(FunctionType f)
-    requires((AK::IsFunctionPointer<FunctionType> && IsCallableWithArguments<RemovePointer<FunctionType>, In...> && !IsSame<RemoveCVReference<FunctionType>, SafeFunction>))
+    requires((AK::IsFunctionPointer<FunctionType> && IsCallableWithArguments<RemovePointer<FunctionType>, Out, In...> && !IsSame<RemoveCVReference<FunctionType>, SafeFunction>))
     {
         init_with_callable(move(f), CallableKind::FunctionPointer);
     }
@@ -85,7 +85,7 @@ public:
 
     template<typename CallableType>
     SafeFunction& operator=(CallableType&& callable)
-    requires((AK::IsFunctionObject<CallableType> && IsCallableWithArguments<CallableType, In...>))
+    requires((AK::IsFunctionObject<CallableType> && IsCallableWithArguments<CallableType, Out, In...>))
     {
         clear();
         init_with_callable(forward<CallableType>(callable));
@@ -94,7 +94,7 @@ public:
 
     template<typename FunctionType>
     SafeFunction& operator=(FunctionType f)
-    requires((AK::IsFunctionPointer<FunctionType> && IsCallableWithArguments<RemovePointer<FunctionType>, In...>))
+    requires((AK::IsFunctionPointer<FunctionType> && IsCallableWithArguments<RemovePointer<FunctionType>, Out, In...>))
     {
         clear();
         if (f)
diff --git a/Userland/Libraries/LibXML/Parser/Parser.cpp b/Userland/Libraries/LibXML/Parser/Parser.cpp
index ea348178e8..334b82a61e 100644
--- a/Userland/Libraries/LibXML/Parser/Parser.cpp
+++ b/Userland/Libraries/LibXML/Parser/Parser.cpp
@@ -242,7 +242,7 @@ ErrorOr<void, ParseError> Parser::expect(StringView expected)
 }
 
 template<typename Pred>
-requires(IsCallableWithArguments<Pred, char>) ErrorOr<StringView, ParseError> Parser::expect(Pred predicate, StringView description)
+requires(IsCallableWithArguments<Pred, bool, char>) ErrorOr<StringView, ParseError> Parser::expect(Pred predicate, StringView description)
 {
     auto rollback = rollback_point();
     auto start = m_lexer.tell();
@@ -257,7 +257,7 @@ requires(IsCallableWithArguments<Pred, char>) ErrorOr<StringView, ParseError> Pa
 }
 
 template<typename Pred>
-requires(IsCallableWithArguments<Pred, char>) ErrorOr<StringView, ParseError> Parser::expect_many(Pred predicate, StringView description)
+requires(IsCallableWithArguments<Pred, bool, char>) ErrorOr<StringView, ParseError> Parser::expect_many(Pred predicate, StringView description)
 {
     auto rollback = rollback_point();
     auto start = m_lexer.tell();
diff --git a/Userland/Libraries/LibXML/Parser/Parser.h b/Userland/Libraries/LibXML/Parser/Parser.h
index fc6f39714b..eec1b01e19 100644
--- a/Userland/Libraries/LibXML/Parser/Parser.h
+++ b/Userland/Libraries/LibXML/Parser/Parser.h
@@ -139,9 +139,9 @@ private:
 
     ErrorOr<void, ParseError> expect(StringView);
     template<typename Pred>
-    requires(IsCallableWithArguments<Pred, char>) ErrorOr<StringView, ParseError> expect(Pred, StringView description);
+    requires(IsCallableWithArguments<Pred, bool, char>) ErrorOr<StringView, ParseError> expect(Pred, StringView description);
     template<typename Pred>
-    requires(IsCallableWithArguments<Pred, char>) ErrorOr<StringView, ParseError> expect_many(Pred, StringView description);
+    requires(IsCallableWithArguments<Pred, bool, char>) ErrorOr<StringView, ParseError> expect_many(Pred, StringView description);
 
     static size_t s_debug_indent_level;
     [[nodiscard]] auto rollback_point(SourceLocation location = SourceLocation::current())