diff --git a/src/random.cpp b/src/random.cpp
--- a/src/random.cpp
+++ b/src/random.cpp
@@ -295,8 +295,10 @@
 /**
  * Fallback: get 32 bytes of system entropy from /dev/urandom. The most
  * compatible way to get cryptographic randomness on UNIX-ish platforms.
+ *
+ * This function is defined but unused on OpenBSD, MAC_OSX and FreeBSD.
  */
-static void GetDevURandom(uint8_t *ent32) {
+[[maybe_unused]] static void GetDevURandom(uint8_t *ent32) {
     int f = open("/dev/urandom", O_RDONLY);
     if (f == -1) {
         RandFailure();