diff --git a/packages/dune/package.py b/packages/dune/package.py
index 54617b8..4621eac 100644
--- a/packages/dune/package.py
+++ b/packages/dune/package.py
@@ -263,13 +263,15 @@ class Dune(CMakePackage):
     def cmake(self, spec, prefix):
         if self.stage.archive_file:
             os.remove(self.stage.archive_file)
-        optFile = open(join_path(self.stage.source_path, "..", "dune.opts"), "w")
-        optFile.write('CMAKE_FLAGS="')
-        for flag in self.cmake_args():
-            optFile.write(flag.replace("\"", "'")+" ")
-        optFile.write('-DCMAKE_INSTALL_PREFIX=%s' % prefix)
-        optFile.write('"')
-        optFile.close()
+
+        # Write an opts file for later use
+        with open(join_path(self.stage.source_path, "..", "dune.opts"), "w") as optFile:
+            optFile.write('CMAKE_FLAGS="')
+            for flag in self.cmake_args():
+                optFile.write(flag.replace("\"", "'")+" ")
+            optFile.write('-DCMAKE_INSTALL_PREFIX=%s' % prefix)
+            optFile.write('"')
+
         set_executable('bin/dunecontrol')
         installer = Executable('bin/dunecontrol')
         options_file = join_path(self.stage.source_path, "..", "dune.opts")