diff --git a/tools/sky/serialdump.c b/tools/sky/serialdump.c
index 447999026..d0e7fac3c 100644
--- a/tools/sky/serialdump.c
+++ b/tools/sky/serialdump.c
@@ -164,8 +164,11 @@ main(int argc, char **argv)
   }
   fprintf(stderr, "connecting to %s (%s)", device, speedname);
 
-#ifndef __APPLE__
+#ifdef O_SYNC
   fd = open(device, O_RDWR | O_NOCTTY | O_NDELAY | O_DIRECT | O_SYNC);
+  if(fd < 0 && errno == EINVAL){ // O_SYNC not supported (e.g. raspberian)
+    fd = open(device, O_RDWR | O_NOCTTY | O_NDELAY | O_DIRECT);
+  }
 #else
   fd = open(device, O_RDWR | O_NOCTTY | O_NDELAY | O_SYNC );
 #endif