diff --git a/cfg/avr.cfg b/cfg/avr.cfg
index 72cfa3f3a..e57a941dc 100644
--- a/cfg/avr.cfg
+++ b/cfg/avr.cfg
@@ -103,7 +103,7 @@
   <define name="M_2_SQRTPI" value="1.12837916709551257390"/>
   <define name="M_SQRT2" value="1.41421356237309504880"/>
   <define name="M_SQRT1_2" value="0.70710678118654752440"/>
-  <!--define name="NAN" value="__builtin_nan(\”\”)"/-->
+  <define name="NAN" value="__builtin_nan(\”\”)"/>
   <define name="powf" value="pow"/>
   <define name="roundf" value="round"/>
   <define name="signbitf" value="signbit"/>