diff --git a/server/src/bin/lesavka-uvc.rs b/server/src/bin/lesavka-uvc.rs
index 99606f9..b51b8c1 100644
--- a/server/src/bin/lesavka-uvc.rs
+++ b/server/src/bin/lesavka-uvc.rs
@@ -120,6 +120,8 @@ fn main() -> Result<()> {
     );
 
     let debug = env::var("LESAVKA_UVC_DEBUG").is_ok();
+    let nonblock = env::var("LESAVKA_UVC_BLOCKING").is_err();
+    eprintln!("[lesavka-uvc] nonblock={}", if nonblock { 1 } else { 0 });
     let mut setup_seen: u64 = 0;
     let mut data_seen: u64 = 0;
     let mut dq_err_seen: u64 = 0;
@@ -302,10 +304,11 @@ fn read_interface(path: &str) -> Option<u8> {
 }
 
 fn open_with_retry(path: &str) -> Result<std::fs::File> {
+    let nonblock = env::var("LESAVKA_UVC_BLOCKING").is_err();
     for attempt in 1..=200 {
         let mut opts = OpenOptions::new();
         opts.read(true).write(true);
-        if env::var("LESAVKA_UVC_NONBLOCK").is_ok() {
+        if nonblock {
             opts.custom_flags(libc::O_NONBLOCK);
         }
         match opts.open(path) {