diff --git a/platformio.ini b/platformio.ini
index 42c1088..af24af1 100644
--- a/platformio.ini
+++ b/platformio.ini
@@ -18,8 +18,9 @@ board_build.filesystem = littlefs
 monitor_speed = 115200
 upload_speed = 921600
 ;monitor_filters = send_on_enter
-build_src_filter = 
-	+<meshberry/> 
+extra_scripts = pre:scripts/git_version.py
+build_src_filter =
+	+<meshberry/>
 	-<chat-relay/>
 lib_deps =
 	lovyan03/LovyanGFX @ ^1.2
diff --git a/scripts/git_version.py b/scripts/git_version.py
new file mode 100644
index 0000000..bf19bb4
--- /dev/null
+++ b/scripts/git_version.py
@@ -0,0 +1,19 @@
+Import("env")
+
+import subprocess
+
+
+def git(*args):
+    try:
+        return subprocess.check_output(
+            ["git"] + list(args), stderr=subprocess.DEVNULL
+        ).strip().decode("ascii")
+    except Exception:
+        return None
+
+# count number of commits.
+build_number = git("rev-list", "--count", "HEAD") or "0"
+
+env.Append(BUILD_FLAGS=[
+    "-DBUILD_NUMBER=%s" % build_number
+])
diff --git a/src/meshberry/main.cpp b/src/meshberry/main.cpp
index de6d223..1bd73e6 100644
--- a/src/meshberry/main.cpp
+++ b/src/meshberry/main.cpp
@@ -11,8 +11,14 @@
 
 BleKeyboard bleKeyboard;
 
+#ifndef BUILD_NUMBER
+#define BUILD_NUMBER 0
+#endif
+
 void setup() {
     Serial.begin(SERIAL_BAUD);
+    Serial.printf("Build #%d\n", BUILD_NUMBER);
+
     esp_sleep_wakeup_cause_t cause = esp_sleep_get_wakeup_cause();
     if (cause == ESP_SLEEP_WAKEUP_EXT1 || cause == ESP_SLEEP_WAKEUP_TOUCHPAD) {
         Serial.println("[wake] resumed from deep sleep");