diff --git a/src/sig/picnic/external/oqs_picnic_macros.h b/src/sig/picnic/external/oqs_picnic_macros.h
index 5910d22e1b..c069f5ee1e 100644
--- a/src/sig/picnic/external/oqs_picnic_macros.h
+++ b/src/sig/picnic/external/oqs_picnic_macros.h
@@ -4,7 +4,9 @@
 #include <oqs/common.h>
 
 /* avoid printing debug output */
+#ifndef NDEBUG
 #define NDEBUG
+#endif
 
 /* use OQS's free function */
 #define free OQS_MEM_insecure_free