diff --git a/cmd_parser.c b/cmd_parser.c
index 9e2be41..a1e187e 100644
--- a/cmd_parser.c
+++ b/cmd_parser.c
@@ -273,7 +273,9 @@ void parse_lag(void)
 
 	if (cmd_words_len < 2 || !isnumber(cmd_buffer[cmd_words_b[1]]))
 		goto err;
-	group = cmd_buffer[cmd_words_b[1]] - '0';
+	group = cmd_buffer[cmd_words_b[1]] - '1';
+	if (group > 3)		/* '0' wraps well past three, so one test does both ends */
+		goto err;
 
 	uint8_t w = 2;
 	while (w < cmd_words_len) {
@@ -283,7 +285,9 @@ void parse_lag(void)
 			port = cmd_buffer[cmd_words_b[w]] - '1';
 			if (isnumber(cmd_buffer[cmd_words_b[w] + 1]))
 				port = (port + 1) * 10 + cmd_buffer[cmd_words_b[w] + 1] - '1';
-				port = machine.phys_to_log_port[port];
+			if (port > 8)	/* phys_to_log_port holds nine entries */
+				goto err;
+			port = machine.phys_to_log_port[port];
 		} else {
 			goto err;
 		}
@@ -295,7 +299,7 @@ void parse_lag(void)
 	port_lag_members_set(group, members);
 	return;
 err:
-	print_string("Error: lag <lag> [port]...\n");
+	print_string("Error: lag <1-4> [port]...\n");
 }
 
 
@@ -304,7 +308,11 @@ void parse_lag_hash(void)
 	__xdata uint8_t group;
 	__xdata uint8_t hash = 0;
 
-	group = cmd_buffer[cmd_words_b[1]] - '0';
+	if (cmd_words_len < 2 || !isnumber(cmd_buffer[cmd_words_b[1]]))
+		goto err;
+	group = cmd_buffer[cmd_words_b[1]] - '1';
+	if (group > 3)		/* '0' wraps well past three, so one test does both ends */
+		goto err;
 
 	uint8_t w = 2;
 	while (w < cmd_words_len) {
@@ -330,6 +338,9 @@ void parse_lag_hash(void)
 		w++;
 	}
 	port_lag_hash_set(group, hash);
+	return;
+err:
+	print_string("Error: lag hash <1-4> [type]...\n");
 }
 
 
diff --git a/rtl837x_port.c b/rtl837x_port.c
index 9388cc6..a85e90d 100644
--- a/rtl837x_port.c
+++ b/rtl837x_port.c
@@ -758,7 +758,7 @@ void port_lag_members_set(__xdata uint8_t lag, __xdata uint16_t members) __banke
 	print_string("port_lag_members_set, lag: "); print_byte(lag); print_string(", members: "); print_short(members);
 	write_char('\n');
 	if (lag > 3) {
-		print_string("Link aggregation group must be 0-3!\n");
+		print_string("Link aggregation group out of range\n");
 		return;
 	}
 	reg_read_m(RTL837X_TRK_HASH_CTRL_BASE + (lag << 2));
@@ -777,8 +777,10 @@ void port_lag_hash_set(__xdata uint8_t lag, __xdata uint8_t hash_bits) __banked
 {
 	print_string("port_lag_hash_set, lag: "); print_byte(lag); print_string(", hash: "); print_byte(hash_bits);
 	write_char('\n');
-	if (lag > 3)
-		print_string("Link aggregation group must be 0-3!\n");
+	if (lag > 3) {
+		print_string("Link aggregation group out of range\n");
+		return;
+	}
 	REG_WRITE(RTL837X_TRK_HASH_CTRL_BASE + (lag << 2), 0, 0, 0, hash_bits);
 }