diff --git a/libraries/AC_PID/AC_PID.cpp b/libraries/AC_PID/AC_PID.cpp
index 9baa3cc14f..4beb52fa9d 100644
--- a/libraries/AC_PID/AC_PID.cpp
+++ b/libraries/AC_PID/AC_PID.cpp
@@ -1,4 +1,4 @@
-// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: t -*-
+// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
 
 /// @file	AC_PID.cpp
 /// @brief	Generic PID algorithm
diff --git a/libraries/AC_PID/AC_PID.h b/libraries/AC_PID/AC_PID.h
index 8fc20c8685..b774b779ef 100644
--- a/libraries/AC_PID/AC_PID.h
+++ b/libraries/AC_PID/AC_PID.h
@@ -1,4 +1,4 @@
-// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: t -*-
+// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
 
 /// @file	AC_PID.h
 /// @brief	Generic PID algorithm, with EEPROM-backed storage of constants.