diff --git a/AK/Forward.h b/AK/Forward.h
index c0bbdbfddc..c1dccb3f55 100644
--- a/AK/Forward.h
+++ b/AK/Forward.h
@@ -109,6 +109,12 @@ class NonnullRefPtr;
 template<typename T>
 class NonnullOwnPtr;
 
+template<typename T, int inline_capacity = 0>
+class NonnullRefPtrVector;
+
+template<typename T, int inline_capacity = 0>
+class NonnullOwnPtrVector;
+
 template<typename T>
 class Optional;
 
@@ -154,7 +160,9 @@ using AK::JsonObject;
 using AK::JsonValue;
 using AK::LogStream;
 using AK::NonnullOwnPtr;
+using AK::NonnullOwnPtrVector;
 using AK::NonnullRefPtr;
+using AK::NonnullRefPtrVector;
 using AK::Optional;
 using AK::OutputMemoryStream;
 using AK::OutputStream;
diff --git a/AK/NonnullOwnPtrVector.h b/AK/NonnullOwnPtrVector.h
index ae4aca2954..f42487e33e 100644
--- a/AK/NonnullOwnPtrVector.h
+++ b/AK/NonnullOwnPtrVector.h
@@ -31,7 +31,7 @@
 
 namespace AK {
 
-template<typename T, int inline_capacity = 0>
+template<typename T, int inline_capacity>
 class NonnullOwnPtrVector : public NonnullPtrVector<NonnullOwnPtr<T>, inline_capacity> {
 };
 
diff --git a/AK/NonnullRefPtrVector.h b/AK/NonnullRefPtrVector.h
index 9becc30165..1842099be3 100644
--- a/AK/NonnullRefPtrVector.h
+++ b/AK/NonnullRefPtrVector.h
@@ -31,7 +31,7 @@
 
 namespace AK {
 
-template<typename T, int inline_capacity = 0>
+template<typename T, int inline_capacity>
 class NonnullRefPtrVector : public NonnullPtrVector<NonnullRefPtr<T>, inline_capacity> {
 };