diff --git a/tool/run b/tool/run
index 8372823a0..e74c0fba6 100755
--- a/tool/run
+++ b/tool/run
@@ -887,24 +887,28 @@ proc spawn_serial { wait_for_re timeout_value kernel_msg } {
 			jtag_load
 		}
 
-		# pipe the serial output through 'tr', sometimes expect steps out due to
-		# unexpected pipe behaviour and reports EOF although the pipe is still active
-		eval spawn sh -c \"$serial_cmd | tr a a\"
-		set serial_spawn_id $spawn_id
-
 		set timeout 210
-		expect {
-			$kernel_msg  { break; }
-			eof     { puts stderr "Serial command process died unexpectedly"; incr retry -1; }
-			timeout { puts stderr "Boot process timed out"; close; incr retry -1; }
+		while {true} {
+			eval spawn $serial_cmd
+			set serial_spawn_id $spawn_id
+			expect {
+				$kernel_msg  {
+					wait_for_output $wait_for_re $timeout_value $serial_spawn_id;
+					return;
+				}
+				eof          { continue; }
+				timeout      {
+					puts stderr "Boot process timed out";
+					close;
+					incr retry -1;
+					break;
+				}
+			}
 		}
 	}
-	if { $retry == 0 } {
-		puts stderr "Boot process failed 3 times in series. I give up!";
-		exit -1;
-	}
 
-	wait_for_output $wait_for_re $timeout_value $serial_spawn_id
+	puts stderr "Boot process failed 3 times in series. I give up!";
+	exit -1;
 }