diff --git a/lib_cxng/src/cx_hkdf.c b/lib_cxng/src/cx_hkdf.c
index 54095c8a0..20224b560 100644
--- a/lib_cxng/src/cx_hkdf.c
+++ b/lib_cxng/src/cx_hkdf.c
@@ -31,7 +31,7 @@ void cx_hkdf_extract(const cx_md_t hash_id, const unsigned char* ikm, unsigned i
 
 }
 
-void cx_hkdf_expand(const cx_md_t hash_id, const unsigned char *prk, unsigned int prk_len, unsigned char *info,
+void cx_hkdf_expand(const cx_md_t hash_id, const unsigned char *prk, unsigned int prk_len, const unsigned char *info,
                    unsigned int info_len, unsigned char *okm, unsigned int okm_len) {
   unsigned char         i;
   unsigned int          offset = 0;
diff --git a/lib_cxng/src/cx_hkdf.h b/lib_cxng/src/cx_hkdf.h
index af573c3d0..049de8f1a 100644
--- a/lib_cxng/src/cx_hkdf.h
+++ b/lib_cxng/src/cx_hkdf.h
@@ -5,7 +5,7 @@
 
 void cx_hkdf_extract(const cx_md_t hash_id, const unsigned char *ikm, unsigned int ikm_len, unsigned char *salt,
                      unsigned int salt_len, unsigned char *prk);
-void cx_hkdf_expand(const cx_md_t hash_id, const unsigned char *prk, unsigned int prk_len, unsigned char *info,
+void cx_hkdf_expand(const cx_md_t hash_id, const unsigned char *prk, unsigned int prk_len, const unsigned char *info,
                     unsigned int info_len, unsigned char *okm, unsigned int okm_len);
 
 #endif // CX_HKDF_H