diff --git a/drygascon/Implementations/crypto_aead/drygascon128/add_arm_cortex-m/drygascon128_arm_selector.h b/drygascon/Implementations/crypto_aead/drygascon128/add_arm_cortex-m/drygascon128_arm_selector.h
index fb2275a..eac7339 100644
--- a/drygascon/Implementations/crypto_aead/drygascon128/add_arm_cortex-m/drygascon128_arm_selector.h
+++ b/drygascon/Implementations/crypto_aead/drygascon128/add_arm_cortex-m/drygascon128_arm_selector.h
@@ -45,4 +45,8 @@
         #define DRYGASCON_ALIGN_INPUT_32
 #endif
 
+#ifndef __DRYGASCON_ARM_SELECTOR_FOUND__
+#error "No ARM definition found"
+#endif
+
 #endif