diff --git a/common/CMakeLists.txt b/common/CMakeLists.txt
index 630535f201..ef1d8896c7 100644
--- a/common/CMakeLists.txt
+++ b/common/CMakeLists.txt
@@ -194,6 +194,7 @@ set( KICOMMON_SRCS
     wildcards_and_files_ext.cpp
     wx_filename.cpp
 
+    singleton.cpp
     pgm_base.cpp
 
     ../scripting/python_scripting.cpp
diff --git a/common/singleton.cpp b/common/singleton.cpp
new file mode 100644
index 0000000000..dba002c22a
--- /dev/null
+++ b/common/singleton.cpp
@@ -0,0 +1,43 @@
+/*
+ * This program source code file is part of KiCad, a free EDA CAD application.
+ *
+ * Copyright The KiCad Developers, see AUTHORS.txt for contributors.
+ *
+ * This program is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation, either version 3 of the License, or (at your
+ * option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <singleton.h>
+#include <bs_thread_pool.hpp>
+#include <gal/opengl/gl_context_mgr.h>
+
+
+KICAD_SINGLETON::~KICAD_SINGLETON()
+{
+    // This will wait for all threads to finish and then join them to the main thread
+    delete m_ThreadPool;
+
+    m_ThreadPool = nullptr;
+
+    m_GLContextManager->DeleteAll();
+    delete m_GLContextManager;
+    m_GLContextManager = nullptr;
+}
+
+
+void KICAD_SINGLETON::Init()
+{
+    int num_threads = std::max( 0, ADVANCED_CFG::GetCfg().m_MaximumThreads );
+    m_ThreadPool = new BS::thread_pool( num_threads );
+    m_GLContextManager = new GL_CONTEXT_MANAGER();
+}
\ No newline at end of file
diff --git a/include/singleton.h b/include/singleton.h
index f24c1454e3..c9c1ef3991 100644
--- a/include/singleton.h
+++ b/include/singleton.h
@@ -21,37 +21,25 @@
 #define KICAD_SINGLETON_H
 
 #include <advanced_config.h>
-#include <bs_thread_pool.hpp>
-#include <gal/opengl/gl_context_mgr.h>
+
+class GL_CONTEXT_MANAGER;
+namespace BS
+{
+class thread_pool;
+}
 
 class KICAD_SINGLETON
 {
 public:
     KICAD_SINGLETON(){};
 
-    ~KICAD_SINGLETON()
-    {
-        // This will wait for all threads to finish and then join them to the main thread
-        delete m_ThreadPool;
-
-        m_ThreadPool = nullptr;
-
-        m_GLContextManager->DeleteAll();
-        delete m_GLContextManager;
-        m_GLContextManager = nullptr;
-    };
+    ~KICAD_SINGLETON();
 
 
-    void Init()
-    {
-        int num_threads = std::max( 0, ADVANCED_CFG::GetCfg().m_MaximumThreads );
-        m_ThreadPool = new BS::thread_pool( num_threads );
-        m_GLContextManager = new GL_CONTEXT_MANAGER();
-    }
+    void Init();
 
     BS::thread_pool* m_ThreadPool;
     GL_CONTEXT_MANAGER* m_GLContextManager;
-
 };
 
 
diff --git a/qa/tests/pcbnew/test_module.cpp b/qa/tests/pcbnew/test_module.cpp
index 99c951f61c..fa7ba82487 100644
--- a/qa/tests/pcbnew/test_module.cpp
+++ b/qa/tests/pcbnew/test_module.cpp
@@ -32,7 +32,7 @@
 
 #include <wx/image.h>
 #include <wx/init.h>
-
+#include <wx/app.h>
 
 bool init_unit_test()
 {