diff --git a/src/c2espcommon.c b/src/c2espcommon.c
index 51291f7..409e7f6 100644
--- a/src/c2espcommon.c
+++ b/src/c2espcommon.c
@@ -43,11 +43,11 @@
  * Globals...
  */
 char		CallerName[50];  	/* String that identifies the calling program */
-int		DoBack;			/* Enables the back channel comms */ 
+extern int	DoBack;			/* Enables the back channel comms */
 char 		BackBuf[32000]; //for the back channel replies from the printer
 int 		BackBufLen=sizeof(BackBuf)-1;
 FILE 		*LogFile = NULL; //file descriptor for log file
-time_t		StartTime;
+extern time_t	StartTime;
 int		BlackPercent, ColourPercent;
 
 time_t KeepAwake(time_t Start, int Interval, FILE *PrintFile)
diff --git a/src/c2espcommon.h b/src/c2espcommon.h
index b726204..967e9ce 100644
--- a/src/c2espcommon.h
+++ b/src/c2espcommon.h
@@ -35,8 +35,8 @@
 /*
  * Globals...
 */
-char 		BackBuf[32000]; //for the back channel replies from the printer
-int		ColourPercent, BlackPercent; //to store the detected marker levels
+extern char 	BackBuf[32000]; //for the back channel replies from the printer
+extern int	ColourPercent, BlackPercent; //to store the detected marker levels
 
 
 time_t KeepAwake(time_t Start, int Interval, FILE *PrintFile);