diff --git a/src/ambientocclusionbaker.cpp b/src/ambientocclusionbaker.cpp
index d2714c4d..5e935472 100644
--- a/src/ambientocclusionbaker.cpp
+++ b/src/ambientocclusionbaker.cpp
@@ -1,6 +1,7 @@
 #include <QOpenGLFramebufferObjectFormat>
 #include <QThread>
 #include <QDebug>
+#include <QtGlobal>
 #define LIGHTMAPPER_IMPLEMENTATION
 #include "qtlightmapper.h"
 #include "ambientocclusionbaker.h"
@@ -15,8 +16,9 @@ AmbientOcclusionBaker::AmbientOcclusionBaker(QScreen *targetScreen) :
     m_bakeHeight(256),
     m_ambientOcclusionImage(nullptr)
 {
+#if QT_VERSION >= QT_VERSION_CHECK(5, 6, 0)
     m_useCore = QSurfaceFormat::defaultFormat().profile() == QSurfaceFormat::CoreProfile;
-    
+#endif
     create();
     m_context = new QOpenGLContext();
     
@@ -62,6 +64,7 @@ void AmbientOcclusionBaker::setRenderThread(QThread *thread)
 
 void AmbientOcclusionBaker::bake()
 {
+#if QT_VERSION >= QT_VERSION_CHECK(5, 6, 0)
     if (m_meshResultContext.parts().empty())
         return;
     
@@ -213,4 +216,5 @@ void AmbientOcclusionBaker::bake()
     free(sceneNormals);
 
     m_context->doneCurrent();
+#endif
 }
diff --git a/src/ambientocclusionbaker.h b/src/ambientocclusionbaker.h
index 7a6edfc6..38437c64 100644
--- a/src/ambientocclusionbaker.h
+++ b/src/ambientocclusionbaker.h
@@ -10,7 +10,11 @@
 #include "meshresultcontext.h"
 #include "meshloader.h"
 
+#if QT_VERSION >= QT_VERSION_CHECK(5, 6, 0)
 class AmbientOcclusionBaker : QOffscreenSurface, public QtLightMapper
+#else
+class AmbientOcclusionBaker : QOffscreenSurface
+#endif
 {
 public:
 	AmbientOcclusionBaker(QScreen *targetScreen = Q_NULLPTR);
diff --git a/src/gltffile.cpp b/src/gltffile.cpp
index 2383ecf7..12070731 100644
--- a/src/gltffile.cpp
+++ b/src/gltffile.cpp
@@ -6,7 +6,7 @@
 #include <QDir>
 #include "gltffile.h"
 #include "version.h"
-#include "util.h"
+#include "dust3dutil.h"
 
 // Play with glTF online:
 // https://gltf-viewer.donmccurdy.com/
diff --git a/src/qtlightmapper.h b/src/qtlightmapper.h
index 7754b8f4..ae594c0a 100644
--- a/src/qtlightmapper.h
+++ b/src/qtlightmapper.h
@@ -15,6 +15,8 @@
 * you are granted a perpetual, irrevocable license to copy *
 * and modify this file however you want.                   *
 ***********************************************************/
+#include <QtGlobal>
+#if QT_VERSION >= QT_VERSION_CHECK(5, 6, 0)
 
 #ifndef QT_LIGHTMAPPER_H
 #define QT_LIGHTMAPPER_H
@@ -166,10 +168,10 @@ GLuint loadShader(GLenum type, const char *source);
 
 #include <stdlib.h>
 #include <stdio.h>
-#include <math.h>
 #include <float.h>
 #include <assert.h>
 #include <limits.h>
+#include <cmath>
 
 #define LM_SWAP(type, a, b) { type tmp = (a); (a) = (b); (b) = tmp; }
 
@@ -180,7 +182,7 @@ GLuint loadShader(GLenum type, const char *source);
 #if defined(_MSC_VER) && (_MSC_VER <= 1700)
 static inline lm_bool lm_finite(float a) { return _finite(a); }
 #else
-static inline lm_bool lm_finite(float a) { return isfinite(a); }
+static inline lm_bool lm_finite(float a) { return std::isfinite(a); }
 #endif
 
 static inline int      lm_mini      (int     a, int     b) { return a < b ? a : b; }
@@ -2087,3 +2089,5 @@ void QtLightMapper::destroyScene(scene_t *scene)
 }
 
 #endif // LIGHTMAPPER_IMPLEMENTATION
+
+#endif
diff --git a/thirdparty/thekla_atlas/src/nvcore/Memory.cpp b/thirdparty/thekla_atlas/src/nvcore/Memory.cpp
index 0ebd009d..03b05dfc 100755
--- a/thirdparty/thekla_atlas/src/nvcore/Memory.cpp
+++ b/thirdparty/thekla_atlas/src/nvcore/Memory.cpp
@@ -5,6 +5,10 @@
 #include "Utils.h"
 
 #include <stdlib.h>
+#if defined(__APPLE__)
+#else
+#include <malloc.h>
+#endif
 
 #define USE_EFENCE 0
 
diff --git a/thirdparty/thekla_atlas/src/nvmath/Box.h b/thirdparty/thekla_atlas/src/nvmath/Box.h
index a7c8b15e..bec04784 100755
--- a/thirdparty/thekla_atlas/src/nvmath/Box.h
+++ b/thirdparty/thekla_atlas/src/nvmath/Box.h
@@ -99,7 +99,7 @@ namespace nv
 
 } // nv namespace
 
-#include "box.inl"
+#include "Box.inl"
 
 
 #endif // NV_MATH_BOX_H