diff --git a/niimprint/__main__.py b/niimprint/__main__.py
index 4cdaae0..e8500a6 100644
--- a/niimprint/__main__.py
+++ b/niimprint/__main__.py
@@ -1,3 +1,4 @@
+import logging
 import re
 
 import click
@@ -51,7 +52,18 @@ from niimprint import BluetoothTransport, PrinterClient, SerialTransport
     required=True,
     help="Image path",
 )
-def print_cmd(model, conn, addr, density, rotate, image):
+@click.option(
+    "-v",
+    "--verbose",
+    is_flag=True,
+    help="Enable verbose logging",
+)
+def print_cmd(model, conn, addr, density, rotate, image, verbose):
+    logging.basicConfig(
+        level="DEBUG" if verbose else "INFO",
+        format="%(levelname)s | %(module)s:%(funcName)s:%(lineno)d - %(message)s",
+    )
+
     if conn == "bluetooth":
         assert conn is not None, "--addr argument required for bluetooth connection"
         addr = addr.upper()
diff --git a/niimprint/printer.py b/niimprint/printer.py
index 5f6caef..887d576 100644
--- a/niimprint/printer.py
+++ b/niimprint/printer.py
@@ -82,7 +82,7 @@ class SerialTransport(BaseTransport):
         if len(all_ports) == 0:
             raise RuntimeError("No serial ports detected")
         if len(all_ports) > 1:
-            msg = "Too many serial ports, please select one via SERIAL_PORT env var:"
+            msg = "Too many serial ports, please select specific one:"
             for port, desc, hwid in all_ports:
                 msg += f"\n- {port} : {desc} [{hwid}]"
             raise RuntimeError(msg)
diff --git a/readme.md b/readme.md
index 74824ee..010e4fb 100644
--- a/readme.md
+++ b/readme.md
@@ -28,6 +28,7 @@ Options:
   -d, --density INTEGER RANGE  Print density  [default: 5; 1<=x<=5]
   -r, --rotate [0|90|180|270]  Image rotation (clockwise)  [default: 0]
   -i, --image PATH             Image path  [required]
+  -v, --verbose                Enable verbose logging
   --help                       Show this message and exit.
 ```