diff --git a/firmware/ChibiOS b/firmware/ChibiOS
index cf74388693..639f3ea42a 160000
--- a/firmware/ChibiOS
+++ b/firmware/ChibiOS
@@ -1 +1 @@
-Subproject commit cf743886935c39cbf2ca711e54e9e64238da6e57
+Subproject commit 639f3ea42ac1212b03c6a3b04448bab2fa982ad3
diff --git a/simulator/simulator/rusEfiFunctionalTest.cpp b/simulator/simulator/rusEfiFunctionalTest.cpp
index 1d586c9334..042e57d2fc 100644
--- a/simulator/simulator/rusEfiFunctionalTest.cpp
+++ b/simulator/simulator/rusEfiFunctionalTest.cpp
@@ -49,9 +49,9 @@ static void runChprintfTest() {
 
 
 	ts.eos = 0; // reset
-//	chprintf((BaseSequentialStream*)&ts, "%.2f - %.2f", NAN, 0/0);
-//	ts.buffer[ts.eos] = 0;
-//	assertString(testBuffer, "0.23/239.9320/0.1234");
+	chprintf((BaseSequentialStream*)&ts, "%.2f - %.2f", NAN, NAN);
+	ts.buffer[ts.eos] = 0;
+	assertString(testBuffer, "NaN - NaN");
 
 // it's a very, very long and mostly forgotten story how this became our %.2f precision format
 	ts.eos = 0; // reset