diff --git a/AK/Buffered.h b/AK/Buffered.h
index e9e8d44c5fdf2fc9cddc24595ce7d7ba2657affa..f671bd20fac5c92cc6ab410a91a8bd41ad1d5e85 100644
--- a/AK/Buffered.h
+++ b/AK/Buffered.h
@@ -26,7 +26,12 @@
 
 #pragma once
 
+#include <AK/Noncopyable.h>
+#include <AK/Span.h>
+#include <AK/StdLibExtras.h>
 #include <AK/Stream.h>
+#include <AK/Types.h>
+#include <AK/kmalloc.h>
 
 namespace AK {
 
diff --git a/AK/Optional.h b/AK/Optional.h
index 9fcfb1a884355b555f70dd79bd4fd211e1865e14..092cdc6e9f39affd5b4dc4f501f708caa6639f00 100644
--- a/AK/Optional.h
+++ b/AK/Optional.h
@@ -30,6 +30,7 @@
 #include <AK/Platform.h>
 #include <AK/StdLibExtras.h>
 #include <AK/Types.h>
+#include <AK/kmalloc.h>
 
 namespace AK {
 
diff --git a/AK/Singleton.h b/AK/Singleton.h
index ae686a64d2b4c5b5c6ef366e56a1713562915bb3..50a54fe748299c3c80c1e757a412552d70430031 100644
--- a/AK/Singleton.h
+++ b/AK/Singleton.h
@@ -28,6 +28,7 @@
 
 #include <AK/Assertions.h>
 #include <AK/Atomic.h>
+#include <AK/Noncopyable.h>
 #include <AK/kmalloc.h>
 #ifdef KERNEL
 #    include <Kernel/Arch/i386/CPU.h>
diff --git a/AK/SinglyLinkedListWithCount.h b/AK/SinglyLinkedListWithCount.h
index f46daa7a82d289e67e765c04b0d22734194e2324..ec9d0196c9b8c188fbc6082d6eaa5696d4138459 100644
--- a/AK/SinglyLinkedListWithCount.h
+++ b/AK/SinglyLinkedListWithCount.h
@@ -96,12 +96,12 @@ public:
         return List::contains_slow(value);
     }
 
-    using Iterator = List::Iterator;
+    using Iterator = typename List::Iterator;
     friend Iterator;
     Iterator begin() { return List::begin(); }
     Iterator end() { return List::end(); }
 
-    using ConstIterator = List::ConstIterator;
+    using ConstIterator = typename List::ConstIterator;
     friend ConstIterator;
     ConstIterator begin() const { return List::begin(); }
     ConstIterator end() const { return List::end(); }
diff --git a/AK/StackInfo.cpp b/AK/StackInfo.cpp
index 96f06d93bea8de4d9b76721d6a1e487c4c3a3908..fb66f199dccfd4342c543aef4d66fb1ba9b12b61 100644
--- a/AK/StackInfo.cpp
+++ b/AK/StackInfo.cpp
@@ -30,7 +30,7 @@
 
 #ifdef __serenity__
 #    include <serenity.h>
-#elif __linux__ or __APPLE__
+#elif defined(__linux__) or defined(__APPLE__)
 #    include <pthread.h>
 #endif