diff --git a/Userland/Libraries/LibThreading/Thread.cpp b/Userland/Libraries/LibThreading/Thread.cpp
index 0c28d3d51d..632c653ed8 100644
--- a/Userland/Libraries/LibThreading/Thread.cpp
+++ b/Userland/Libraries/LibThreading/Thread.cpp
@@ -52,6 +52,12 @@ ErrorOr<int> Thread::get_priority() const
     return scheduling_parameters.sched_priority;
 }
 
+DeprecatedString Thread::thread_name() const { return m_thread_name; }
+
+pthread_t Thread::tid() const { return m_tid; }
+
+bool Thread::is_started() const { return m_started; }
+
 void Thread::start()
 {
     int rc = pthread_create(
diff --git a/Userland/Libraries/LibThreading/Thread.h b/Userland/Libraries/LibThreading/Thread.h
index 5b3c79973c..5663fbee67 100644
--- a/Userland/Libraries/LibThreading/Thread.h
+++ b/Userland/Libraries/LibThreading/Thread.h
@@ -33,9 +33,9 @@ public:
     template<typename T = void>
     Result<T, ThreadError> join();
 
-    DeprecatedString thread_name() const { return m_thread_name; }
-    pthread_t tid() const { return m_tid; }
-    bool is_started() const { return m_started; }
+    DeprecatedString thread_name() const;
+    pthread_t tid() const;
+    bool is_started() const;
 
 private:
     explicit Thread(Function<intptr_t()> action, StringView thread_name = {});