diff --git a/programs/fileio.c b/programs/fileio.c
index cf3e7414c..c1881a4f0 100644
--- a/programs/fileio.c
+++ b/programs/fileio.c
@@ -1784,6 +1784,8 @@ FIO_compressFilename_srcFile(FIO_ctx_t* const fCtx,
 
 static const char* checked_index(const char* options[], size_t length, size_t index) {
     assert(index < length);
+    // Necessary to avoid warnings since -O3 will omit the above `assert`
+    (void) length;
     return options[index];
 }