diff --git a/main.c b/main.c
index 9950646..37f1895 100644
--- a/main.c
+++ b/main.c
@@ -37,6 +37,8 @@ const char *copyright;
 extern char *optarg;
 extern int optind;
 
+int trace_flag = 0;
+
 void usage()
 {
     fprintf(stderr, "DMR Config, Version %s, %s\n", version, copyright);
diff --git a/radio.h b/radio.h
index 0af4baf..d35960f 100644
--- a/radio.h
+++ b/radio.h
@@ -139,9 +139,9 @@ extern unsigned char radio_mem[];
 //
 // File descriptor of serial port with programming cable attached.
 //
-int radio_port;
+extern int radio_port;
 
 //
 // Read/write progress counter.
 //
-int radio_progress;
+extern int radio_progress;
diff --git a/util.h b/util.h
index 1052bd1..adedad6 100644
--- a/util.h
+++ b/util.h
@@ -35,7 +35,7 @@ extern const char *copyright;
 //
 // Trace data i/o via the serial port.
 //
-int trace_flag;
+extern int trace_flag;
 
 //
 // Print data in hex format.