diff --git a/src/system/kernel/debug/debug.cpp b/src/system/kernel/debug/debug.cpp
index f210c5a999..37c1744c3b 100644
--- a/src/system/kernel/debug/debug.cpp
+++ b/src/system/kernel/debug/debug.cpp
@@ -589,8 +589,8 @@ cmd_shutdown(int argc, char **argv)
 static int
 cmd_help(int argc, char **argv)
 {
-	static const char* usage = "usage: %s\n"
-		"Lists all debugger commands.\n";
+	static const char* usage = "usage: %s [name]\n"
+		"Lists all debugger commands or those starting with \"name\".\n";
 	if (argc > 1 && strcmp(argv[1], "--help") == 0) {
 		kprintf(usage, argv[0]);
 		return 0;
diff --git a/src/system/kernel/debug/debug_parser.cpp b/src/system/kernel/debug/debug_parser.cpp
index 19caf52b5e..383e209e37 100644
--- a/src/system/kernel/debug/debug_parser.cpp
+++ b/src/system/kernel/debug/debug_parser.cpp
@@ -626,9 +626,9 @@ ExpressionParser::_ParseCommand(int& returnCode)
 	if (command == NULL) {
 		if (ambiguous) {
 			snprintf(sTempBuffer, sizeof(sTempBuffer),
-				"Ambiguous command \"%s\". Use tab "
-				"completion to get a list of matching commands. Enter \"help\" "
-				"to get a list of all supported commands.\n", token.string);
+				"Ambiguous command \"%s\". Use tab completion or enter "
+				"\"help %s\" get a list of matching commands.\n", token.string,
+				token.string);
 		} else {
 			snprintf(sTempBuffer, sizeof(sTempBuffer),
 				"Unknown command \"%s\". Enter \"help\" to get a list of "
diff --git a/src/system/kernel/fs/vfs.cpp b/src/system/kernel/fs/vfs.cpp
index 24f54b9370..04659f1fbb 100644
--- a/src/system/kernel/fs/vfs.cpp
+++ b/src/system/kernel/fs/vfs.cpp
@@ -2442,15 +2442,13 @@ dump_vnode(int argc, char **argv)
 static int
 dump_vnodes(int argc, char **argv)
 {
-	if (argc > 2 || !strcmp(argv[1], "--help")) {
+	if (argc != 2 || !strcmp(argv[1], "--help")) {
 		kprintf("usage: %s [device]\n", argv[0]);
 		return 0;
 	}
 
 	// restrict dumped nodes to a certain device if requested
-	dev_t device = -1;
-	if (argc > 1)
-		device = parse_expression(argv[1]);
+	dev_t device = parse_expression(argv[1]);
 
 	struct hash_iterator iterator;
 	struct vnode *vnode;
@@ -2460,7 +2458,7 @@ dump_vnodes(int argc, char **argv)
 
 	hash_open(sVnodeTable, &iterator);
 	while ((vnode = (struct vnode *)hash_next(sVnodeTable, &iterator)) != NULL) {
-		if (device != -1 && vnode->device != device)
+		if (vnode->device != device)
 			continue;
 
 		kprintf("%p%4ld%10Ld%5ld %p %p %p %s%s%s\n", vnode, vnode->device,