diff --git a/src/core/model/system-mutex.h b/src/core/model/system-mutex.h
--- a/src/core/model/system-mutex.h
+++ b/src/core/model/system-mutex.h
@@ -58,6 +58,18 @@
 class SystemMutex 
 {
 public:
+
+#ifndef HAVE_PTHREAD_H
+  // This minimal implementation is needed for to support compilation
+  // of the thread-safe Schedule implementation, on systems without
+  // thread support.
+  
+  /** Constructor */
+  SystemMutex () { };
+  /** Destructor */
+  ~SystemMutex () { };
+
+#else
   SystemMutex ();
   ~SystemMutex ();
 
@@ -74,6 +86,8 @@
 private:
   /** The (system-dependent) implementation. */
   SystemMutexPrivate * m_priv;
+
+#endif /* HAVE_PTHREAD_H */
 };
 
 /**
@@ -118,6 +132,21 @@
 class CriticalSection
 {
 public:
+
+#ifndef HAVE_PTHREAD_H
+  // This minimal implementation is needed for to support compilation
+  // of the thread-safe Schedule implementation, on systems without
+  // thread support.
+
+  /**
+   * Constructor
+   * @param [in] mutex The mutex.
+   */
+  CriticalSection (SystemMutex &mutex) { };
+  /** Destructor */
+  ~CriticalSection () { };
+
+#else /* HAVE_PTHREAD_H */
   /**
    * Construct with the required SystemMutex.
    *
@@ -128,7 +157,10 @@
   ~CriticalSection ();
 private:
   SystemMutex &m_mutex;  /**< The mutex. */
-};
+
+#endif /* HAVE_PTHREAD_H */
+
+};  // class CriticalSection
 
 } // namespace ns3
 
diff --git a/src/core/model/system-thread.h b/src/core/model/system-thread.h
--- a/src/core/model/system-thread.h
+++ b/src/core/model/system-thread.h
@@ -57,10 +57,35 @@
 {
 public:
 
-#ifdef HAVE_PTHREAD_H
+#ifndef HAVE_PTHREAD_H
+  // This minimal implementation is needed for to support compilation
+  // of the thread-safe Schedule implementation, on systems without
+  // thread support.
+
+  /**
+   * Fallback type alias for thread objects
+   * on systems without thread support.
+   */
+  typedef void * ThreadId;
+
+  /**
+   * @brief Returns the default thread Id on systems without thread support.
+   *
+   * @returns Default thread Id. 
+   */
+  static ThreadId Self(void) { return 0; };
+
+  /**
+   * @brief Compares ThreadIds on systems without thread support.
+   *
+   * @param [in] id The ThreadId to compare to.
+   * @returns @c true if @c id matches the current ThreadId.
+   */
+  static bool Equals(ThreadId id) { return true; };
+  
+#else /* HAVE_PTHREAD_H */
   /** Type alias for the system-dependent thread object. */
   typedef pthread_t ThreadId;
-#endif
 
   /**
    * @brief Create a SystemThread object.
@@ -157,7 +182,7 @@
   static bool Equals(ThreadId id);
 
 private:
-#ifdef HAVE_PTHREAD_H
+
   /**
    * Invoke the callback in the new thread.
    *
@@ -168,8 +193,9 @@
 
   Callback<void> m_callback;  /**< The main function for this thread when launched. */
   pthread_t m_thread;  /**< The thread id of the child thread. */
-#endif 
-};
+
+#endif /* HAVE_PTHREAD_H */
+};  // class SystemThread
 
 } // namespace ns3
 
diff --git a/src/core/wscript b/src/core/wscript
--- a/src/core/wscript
+++ b/src/core/wscript
@@ -236,6 +236,13 @@
         'model/watchdog.h',
         'model/synchronizer.h',
         'model/make-event.h',
+        
+        # Include always for compilation
+        # of the thread-safe Schedule implementation,
+        # even on systems without thread support.
+        'model/system-mutex.h',
+        'model/system-thread.h',
+        
         'model/system-wall-clock-ms.h',
         'model/empty.h',
         'model/callback.h',
@@ -350,8 +357,11 @@
         core_test.source.extend(['test/threaded-test-suite.cc'])
         headers.source.extend([
                 'model/unix-fd-reader.h',
-                'model/system-mutex.h',
-                'model/system-thread.h',
+                # Include always for compilation
+                # of the thread-safe Schedule implementation,
+                # on systems without thread support.
+                # 'model/system-mutex.h',
+                # 'model/system-thread.h',
                 'model/system-condition.h',
                 ])