diff --git a/tlsf.c b/tlsf.c
index af575737c7..d6a1e50185 100644
--- a/tlsf.c
+++ b/tlsf.c
@@ -7,6 +7,10 @@
 
 #include "tlsf.h"
 
+#if !defined(_DEBUG)
+#define _DEBUG 0
+#endif
+
 #if defined(__cplusplus)
 #define tlsf_decl inline
 #else
@@ -1046,7 +1050,7 @@ void tlsf_remove_pool(tlsf_t tlsf, pool_t pool)
 */
 
 #if _DEBUG
-int test_ffs_fls()
+static int test_ffs_fls()
 {
 	/* Verify ffs/fls work properly. */
 	int rv = 0;