diff --git a/ext/opencv/extconf.rb b/ext/opencv/extconf.rb
index 03dae4a..951acd2 100755
--- a/ext/opencv/extconf.rb
+++ b/ext/opencv/extconf.rb
@@ -4,6 +4,9 @@ CC = RbConfig::CONFIG['CC']
 if CC =~ /clang/
   RbConfig::MAKEFILE_CONFIG['try_header'] = :try_cpp
   RbConfig::CONFIG['CPP'] = "#{CC} -E"
+elsif RbConfig::CONFIG['arch'] =~ /mswin32/
+  RbConfig::MAKEFILE_CONFIG['try_header'] = :try_cpp
+  RbConfig::CONFIG['CPP'] = "#{CC} /P"
 end
 
 require "mkmf"
@@ -65,15 +68,7 @@ end
 # Check the required headers
 puts ">> Check the required headers..."
 opencv_headers.each {|header|
-  unless have_header(header)
-    if CONFIG["arch"] =~ /mswin32/ and File.exists? "#{incdir}/#{header}"
-      # In mswin32, have_header('opencv2/nonfree/nonfree.hpp') fails because of a syntax problem.
-      warn "warning: #{header} found but `have_header` failed."
-      $defs << "-DHAVE_#{header.tr_cpp}"
-    else
-      raise "#{header} not found."
-    end
-  end
+  raise "#{header} not found." unless have_header(header)
 }
 have_header("stdarg.h")