diff --git a/ext/opencv/extconf.rb b/ext/opencv/extconf.rb
index 7829562..1500fa5 100755
--- a/ext/opencv/extconf.rb
+++ b/ext/opencv/extconf.rb
@@ -33,44 +33,35 @@ opencv_headers = ["opencv2/core/core_c.h", "opencv2/core/core.hpp", "opencv2/img
                   "opencv2/imgproc/imgproc.hpp", "opencv2/video/tracking.hpp", "opencv2/features2d/features2d.hpp",
                   "opencv2/flann/flann.hpp", "opencv2/calib3d/calib3d.hpp", "opencv2/objdetect/objdetect.hpp",
                   "opencv2/legacy/compat.hpp", "opencv2/legacy/legacy.hpp", "opencv2/highgui/highgui_c.h",
-                  "opencv2/highgui/highgui.hpp", "opencv2/photo/photo.hpp", "opencv2/nonfree/nonfree.hpp"]
+                  "opencv2/highgui/highgui.hpp", "opencv2/photo/photo.hpp"]
+opencv_headers_opt = ["opencv2/nonfree/nonfree.hpp"]
 
 opencv_libraries = ["opencv_calib3d", "opencv_contrib", "opencv_core", "opencv_features2d",
-                    "opencv_flann", "opencv_gpu", "opencv_highgui", "opencv_imgproc",
-                    "opencv_legacy", "opencv_ml", "opencv_objdetect", "opencv_video",
-                    "opencv_photo", "opencv_nonfree"]
-
+                    "opencv_flann", "opencv_highgui", "opencv_imgproc", "opencv_legacy",
+                    "opencv_ml", "opencv_objdetect", "opencv_video", "opencv_photo"]
+opencv_libraries_opt = ["opencv_gpu", "opencv_nonfree"]
 
 puts ">> Check the required libraries..."
-case CONFIG["arch"]
-when /mswin32/
+if $mswin or $mingw
   suffix = cv_version_suffix(incdir)
-  opencv_libraries.map! {|lib| lib + suffix }
+  opencv_libraries.map! { |lib| lib + suffix }
+  opencv_libraries_opt.map! { |lib| lib + suffix }
   have_library("msvcrt")
-  opencv_libraries.each {|lib|
-    raise "#{lib}.lib not found." unless have_library(lib)
-  }
-  $CFLAGS << ' /EHsc'
-  CONFIG['CXXFLAGS'] << ' /EHsc'
-when /mingw32/
-  suffix = cv_version_suffix(incdir)
-  opencv_libraries.map! {|lib| lib + suffix }
-  have_library("msvcrt")
-  opencv_libraries.each {|lib|
-    raise "lib#{lib} not found." unless have_library(lib)
-  }
+  if $mswin
+    $CFLAGS << ' /EHsc'
+    CONFIG['CXXFLAGS'] << ' /EHsc'
+  end
 else
-  opencv_libraries.each {|lib|
-    raise "lib#{lib} not found." unless have_library(lib)
-  }
   have_library("stdc++")
 end
 
+opencv_libraries.each { |lib| raise "#{lib} not found." unless have_library(lib) }
+opencv_libraries_opt.each { |lib| warn "#{lib} not found." unless have_library(lib) }
+
 # Check the required headers
 puts ">> Check the required headers..."
-opencv_headers.each {|header|
-  raise "#{header} not found." unless have_header(header)
-}
+opencv_headers.each { |header| raise "#{header} not found." unless have_header(header) }
+opencv_headers_opt.each { |header| warn "#{header} not found." unless have_header(header) }
 have_header("stdarg.h")
 
 if $warnflags
diff --git a/ext/opencv/opencv.cpp b/ext/opencv/opencv.cpp
index 4df2474..de88cf8 100644
--- a/ext/opencv/opencv.cpp
+++ b/ext/opencv/opencv.cpp
@@ -771,6 +771,8 @@ extern "C" {
     */
 #endif
 
+#ifdef HAVE_OPENCV2_NONFREE_NONFREE_HPP
     cv::initModule_nonfree();
+#endif
   }
 }
diff --git a/ext/opencv/opencv.h b/ext/opencv/opencv.h
index 7582687..97dc19f 100644
--- a/ext/opencv/opencv.h
+++ b/ext/opencv/opencv.h
@@ -62,7 +62,6 @@ extern "C" {
 #include "opencv2/video/tracking.hpp"
 #include "opencv2/video/background_segm.hpp"
 #include "opencv2/features2d/features2d.hpp"
-#include "opencv2/nonfree/nonfree.hpp"
 #include "opencv2/flann/flann.hpp"
 #include "opencv2/calib3d/calib3d.hpp"
 #include "opencv2/objdetect/objdetect.hpp"
@@ -79,6 +78,10 @@ extern "C" {
 #include "opencv2/ml/ml.hpp"
 #endif
 
+#ifdef HAVE_OPENCV2_NONFREE_NONFREE_HPP
+#include "opencv2/nonfree/nonfree.hpp"
+#endif
+
 // Ruby/OpenCV headers
 #include "cvutils.h"
 #include "cverror.h"