diff --git a/src/Relays/Relays.h b/src/Relays/Relays.h
index b0712f7..1af8d38 100644
--- a/src/Relays/Relays.h
+++ b/src/Relays/Relays.h
@@ -17,9 +17,9 @@
  * Represents an individual relay.
  */
 typedef struct Relay {
-  void *output_port;
+  volatile void *output_port;
   uint8_t output_pin;
-  void *input_port;
+  volatile void *input_port;
   uint8_t input_pin;
   uint16_t make_time;
   uint16_t break_time;