diff --git a/libs_required/ACG/QtWidgets/QtBaseViewerPicking.cc b/libs_required/ACG/QtWidgets/QtBaseViewerPicking.cc
index 83f73e1fb8303294b4dd6b9cc2f1cc8a63cbc803..172c3376134d54692a6fa9b903db473fec11a68e 100644
--- a/libs_required/ACG/QtWidgets/QtBaseViewerPicking.cc
+++ b/libs_required/ACG/QtWidgets/QtBaseViewerPicking.cc
@@ -57,7 +57,7 @@
 
 
 //== INCLUDES =================================================================
-
+#include <ACG/GL/acg_glew.hh>
 #include "QtBaseViewer.hh"
 #include "QtGLGraphicsScene.hh"
 #include "QtGLGraphicsView.hh"
diff --git a/libs_required/ACG/QtWidgets/QtBaseViewerStereo.cc b/libs_required/ACG/QtWidgets/QtBaseViewerStereo.cc
index 0f20284730880422fd68d4ff0db86d75624d8424..a0708a5b24be9dae1e0abb77d4c63777c86bf502 100644
--- a/libs_required/ACG/QtWidgets/QtBaseViewerStereo.cc
+++ b/libs_required/ACG/QtWidgets/QtBaseViewerStereo.cc
@@ -58,6 +58,7 @@
 
 //== INCLUDES =================================================================
 
+#include <ACG/GL/acg_glew.hh>
 #include "QtBaseViewer.hh"
 #include <QStatusBar>
 #include <QToolButton>
diff --git a/libs_required/ACG/QtWidgets/QtBaseViewerSynchronization.cc b/libs_required/ACG/QtWidgets/QtBaseViewerSynchronization.cc
index 4f24cd07c07d952cb8d692d730f6dbd603b80eac..b2736af94a63f425ef0a0b28d77204d1dbd72373 100644
--- a/libs_required/ACG/QtWidgets/QtBaseViewerSynchronization.cc
+++ b/libs_required/ACG/QtWidgets/QtBaseViewerSynchronization.cc
@@ -57,7 +57,7 @@
 
 
 //== INCLUDES =================================================================
-
+#include <ACG/GL/acg_glew.hh>
 #include "QtBaseViewer.hh"
 #include "QtGLGraphicsScene.hh"
 #include "QtGLGraphicsView.hh"
diff --git a/libs_required/ACG/QtWidgets/QtExaminerViewer.cc b/libs_required/ACG/QtWidgets/QtExaminerViewer.cc
index 6c1a8e0d355715f7aa8b4da1798f8202c9d8eaae..8631537653927409125b2cde3bcb7ffdc0b3c78b 100644
--- a/libs_required/ACG/QtWidgets/QtExaminerViewer.cc
+++ b/libs_required/ACG/QtWidgets/QtExaminerViewer.cc
@@ -57,7 +57,7 @@
 
 
 //== INCLUDES =================================================================
-
+#include <ACG/GL/acg_glew.hh>
 #include "QtExaminerViewer.hh"
 
 #include <QTimer>