diff --git a/ion/src/device/shared/boot/rt0.cpp b/ion/src/device/shared/boot/rt0.cpp
index 8e8f2e39e..45a003f40 100644
--- a/ion/src/device/shared/boot/rt0.cpp
+++ b/ion/src/device/shared/boot/rt0.cpp
@@ -119,5 +119,7 @@ void __attribute__((noinline)) start() {
 }
 
 void __attribute__((interrupt, noinline)) isr_systick() {
-  Ion::Device::Timing::MillisElapsed++;
+  auto t = Ion::Device::Timing::MillisElapsed;
+  t++;
+  Ion::Device::Timing::MillisElapsed = t;
 }