diff --git a/jtag/ChangeLog b/jtag/ChangeLog
index 817f4be9..560a8486 100644
--- a/jtag/ChangeLog
+++ b/jtag/ChangeLog
@@ -1,3 +1,8 @@
+2003-09-10  Marcel Telka  <marcel@telka.sk>
+
+	* src/cmd/dr.c (cmd_dr_run): Added test for missing active instruction and data register (thanks to
+		Mike Tesch for reporting).
+
 2003-09-10  Marcel Telka  <marcel@telka.sk>
 
 	* src/bus/bcm1250.c (bcm1250_bus_printinfo, bcm1250_bus): Fixed typo (compatibile->compatible) in
diff --git a/jtag/THANKS b/jtag/THANKS
index 95e640ac..d23aa151 100644
--- a/jtag/THANKS
+++ b/jtag/THANKS
@@ -16,6 +16,7 @@ Guennadi Liakhovetski
 Brad Parker
 Christian Pellegrin
 Ramses VI
+Mike Tesch
 Holger Schurig
 Matan Ziv-Av
 Alessandro Zummo
diff --git a/jtag/src/cmd/dr.c b/jtag/src/cmd/dr.c
index 36e0592f..655d86a5 100644
--- a/jtag/src/cmd/dr.c
+++ b/jtag/src/cmd/dr.c
@@ -50,7 +50,7 @@ cmd_dr_run( char *params[] )
 	}
 
 	if (chain->active_part >= chain->parts->len) {
-		printf( _("%s: no active part\n"), "part" );
+		printf( _("%s: no active part\n"), "dr" );
 		return 1;
 	}
 
@@ -63,6 +63,15 @@ cmd_dr_run( char *params[] )
 			return -1;
 	}
 
+	if (chain->parts->parts[chain->active_part]->active_instruction == NULL) {
+		printf( _("%s: part without active instruction\n"), "dr" );
+		return 1;
+	}
+	if (chain->parts->parts[chain->active_part]->active_instruction->data_register == NULL) {
+		printf( _("%s: part without active data register\n"), "dr" );
+		return 1;
+	}
+
 	if (dir)
 		r = chain->parts->parts[chain->active_part]->active_instruction->data_register->out;
 	else