diff --git a/lib/hcrypto/bn.h b/lib/hcrypto/bn.h
index 2aa22462b..f3f89b538 100644
--- a/lib/hcrypto/bn.h
+++ b/lib/hcrypto/bn.h
@@ -69,11 +69,11 @@
  *
  */
 
-typedef void BIGNUM;
+typedef struct BIGNUM BIGNUM;
 typedef struct BN_GENCB BN_GENCB;
 typedef struct BN_CTX BN_CTX;
-typedef void BN_MONT_CTX;
-typedef void BN_BLINDING;
+typedef struct BN_MONT_CTX BN_MONT_CTX;
+typedef struct BN_BLINDING BN_BLINDING;
 
 struct BN_GENCB {
     unsigned int ver;