--- a/button.h
+++ b/button.h
@@ -60,8 +60,8 @@
     button_max = 34
 };
 
-char *button_name[button_max];
-int button_code[button_max];
+extern char *button_name[button_max];
+extern int button_code[button_max];
 
 unsigned int speaker_code(unsigned int code);
 
--- a/main.h
+++ b/main.h
@@ -18,9 +18,9 @@
 along with this program; if not, write to the Free Software
 Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 */
-char *midi_device;
+extern char *midi_device;
 
-int delay_sec;
-int delay_usec;
+extern int delay_sec;
+extern int delay_usec;
 
-int string_digit_limit;
+extern int string_digit_limit;