diff --git a/crates/algorithms/algorithms-c/README.md b/crates/algorithms/algorithms-c/README.md
index b543f49..7ddff6e 100755
--- a/crates/algorithms/algorithms-c/README.md
+++ b/crates/algorithms/algorithms-c/README.md
@@ -22,3 +22,5 @@ CC=arm-none-eabi-gcc AR=arm-none-eabi-ar ceedling release
 # compile for this computer
 CC=gcc AR=ar ceedling release
 ```
+
+It is also critically important to define the `-march=ARCH` option when using `arm-none-eabi-gcc`, since the compiler will otherwise just assume a target architecture. In this case, it needs to be set to `armv6-m`, since the MPU is a `cortex-M0+`. This MPU does only support the thumb instructionset, not the ARM32 set.