diff --git a/SConstruct b/SConstruct
index a1267d4e6..88ae94894 100644
--- a/SConstruct
+++ b/SConstruct
@@ -388,7 +388,7 @@ class DXXArchive(DXXCommon):
 	# governed by these arguments.
 	ARGUMENTS = argumentIndirection(['common'])
 	__objects_common = DXXCommon.create_lazy_object_property([os.path.join(srcdir, f) for f in [
-'2d/2dsline.c',
+'2d/2dsline.cpp',
 '2d/bitblt.c',
 '2d/bitmap.c',
 '2d/box.c',
diff --git a/common/2d/2dsline.c b/common/2d/2dsline.cpp
similarity index 100%
rename from common/2d/2dsline.c
rename to common/2d/2dsline.cpp
diff --git a/common/include/gr.h b/common/include/gr.h
index 85271b545..5dc1204d8 100644
--- a/common/include/gr.h
+++ b/common/include/gr.h
@@ -156,6 +156,10 @@ typedef struct _grs_screen {    // This is a video screen
 // grd_curscreen to point to it.  grs_curcanv points to this screen's
 // canvas.  Saves the current VGA state and screen mode.
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 int gr_init(int mode);
 
 int gr_list_modes( u_int32_t gsmodes[] );
@@ -441,4 +445,8 @@ void ogl_do_palfx(void);
 void ogl_init_pixel_buffers(int w, int h);
 void ogl_close_pixel_buffers(void);
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif /* def _GR_H */