diff --git a/src/core/gdbstub.c b/src/core/gdbstub.c
index 213887b5..544595e6 100644
--- a/src/core/gdbstub.c
+++ b/src/core/gdbstub.c
@@ -235,11 +235,14 @@ static void gdbstub_rx_packet ( struct gdbstub *stub ) {
 		case 'M':
 			gdbstub_write_mem ( stub );
 			break;
-		case 'c':
-			gdbstub_continue ( stub, 0 );
-			break;
-		case 's':
-			gdbstub_continue ( stub, 1 );
+		case 'c': /* Continue */
+		case 'k': /* Kill */
+		case 's': /* Step */
+		case 'D': /* Detach */
+			gdbstub_continue ( stub, stub->payload [ 0 ] == 's' );
+			if ( stub->payload [ 0 ] == 'D' ) {
+				gdbstub_send_ok ( stub );
+			}
 			break;
 		default:
 			stub->len = 0;
diff --git a/src/tests/gdbstub_test.S b/src/tests/gdbstub_test.S
index ee594ea8..64783089 100644
--- a/src/tests/gdbstub_test.S
+++ b/src/tests/gdbstub_test.S
@@ -25,5 +25,9 @@ gdbstub_test:
 	int	$3
 	addl	$8, %esp
 
+	/* 5. Step test */
+	int	$3
+	nop
+
 1:
 	jmp	1b
diff --git a/src/tests/gdbstub_test.gdb b/src/tests/gdbstub_test.gdb
index 10db863e..c0c59644 100755
--- a/src/tests/gdbstub_test.gdb
+++ b/src/tests/gdbstub_test.gdb
@@ -71,6 +71,12 @@ define gpxe_test_mem_write
 	gpxe_assert ({char}($esp)) (char)0x99 "gpxe_test_mem_write char"
 end
 
+define gpxe_test_step
+	c
+	si
+	gpxe_assert ({char}($eip-1)) (char)0x90 "gpxe_test_step" # nop = 0x90
+end
+
 gpxe_load_symbols
 gpxe_connect
 gpxe_start_tests
@@ -78,3 +84,4 @@ gpxe_test_regs_read
 gpxe_test_regs_write
 gpxe_test_mem_read
 gpxe_test_mem_write
+gpxe_test_step