diff --git a/src/opus.c b/src/opus.c
index 419918b091457c73ee5ec770553fbc7fc0f1c7cb..55e76d93112a5fd0081f605875a799313c62f66a 100644
--- a/src/opus.c
+++ b/src/opus.c
@@ -31,6 +31,10 @@
 
 #include "opus.h"
 
+#ifndef OPUS_VERSION
+#define OPUS_VERSION "Opus version unknown"
+#endif
+
 const char *opus_strerror(int error)
 {
    static const char *error_strings[8] = {