diff --git a/Kernel/FileSystem/File.h b/Kernel/FileSystem/File.h
index 99574450291..11ab5269fa2 100644
--- a/Kernel/FileSystem/File.h
+++ b/Kernel/FileSystem/File.h
@@ -21,7 +21,7 @@ namespace Kernel {
 
 class File;
 
-class FileBlockCondition : public Thread::BlockCondition {
+class FileBlockCondition final : public Thread::BlockCondition {
 public:
     FileBlockCondition() { }
 
diff --git a/Kernel/FileSystem/Plan9FileSystem.h b/Kernel/FileSystem/Plan9FileSystem.h
index cfc91040be3..105ba05b7a6 100644
--- a/Kernel/FileSystem/Plan9FileSystem.h
+++ b/Kernel/FileSystem/Plan9FileSystem.h
@@ -50,7 +50,7 @@ private:
 
     class Blocker;
 
-    class Plan9FSBlockCondition : public Thread::BlockCondition {
+    class Plan9FSBlockCondition final : public Thread::BlockCondition {
     public:
         Plan9FSBlockCondition(Plan9FS& fs)
             : m_fs(fs)
diff --git a/Kernel/FutexQueue.h b/Kernel/FutexQueue.h
index 57f134ab10e..82076716a16 100644
--- a/Kernel/FutexQueue.h
+++ b/Kernel/FutexQueue.h
@@ -14,7 +14,7 @@
 
 namespace Kernel {
 
-class FutexQueue
+class FutexQueue final
     : public RefCounted<FutexQueue>
     , public Thread::BlockCondition {
 public:
diff --git a/Kernel/Net/Routing.cpp b/Kernel/Net/Routing.cpp
index 84d9933cf65..b75e57d1a3b 100644
--- a/Kernel/Net/Routing.cpp
+++ b/Kernel/Net/Routing.cpp
@@ -55,7 +55,7 @@ private:
     bool m_should_block { true };
 };
 
-class ARPTableBlockCondition : public Thread::BlockCondition {
+class ARPTableBlockCondition final : public Thread::BlockCondition {
 public:
     void unblock(const IPv4Address& ip_addr, const MACAddress& addr)
     {
diff --git a/Kernel/Thread.h b/Kernel/Thread.h
index 8db75a7379d..e2e182718a9 100644
--- a/Kernel/Thread.h
+++ b/Kernel/Thread.h
@@ -1225,7 +1225,7 @@ private:
 
     friend class WaitQueue;
 
-    class JoinBlockCondition : public BlockCondition {
+    class JoinBlockCondition final : public BlockCondition {
     public:
         void thread_did_exit(void* exit_value)
         {
diff --git a/Kernel/WaitQueue.h b/Kernel/WaitQueue.h
index 6e8891128e7..1287da81734 100644
--- a/Kernel/WaitQueue.h
+++ b/Kernel/WaitQueue.h
@@ -12,7 +12,7 @@
 
 namespace Kernel {
 
-class WaitQueue : public Thread::BlockCondition {
+class WaitQueue final : public Thread::BlockCondition {
 public:
     u32 wake_one();
     u32 wake_n(u32 wake_count);