diff --git a/ext/openssl/openssl_missing.c b/ext/openssl/openssl_missing.c
--- a/ext/openssl/openssl_missing.c
+++ b/ext/openssl/openssl_missing.c
@@ -265,7 +265,7 @@
 
 #if !defined(HAVE_BN_RAND_RANGE)
 int
-BN_rand_range(BIGNUM *r, BIGNUM *range)
+BN_rand_range(BIGNUM *r, const BIGNUM *range)
 {
     return bn_rand_range(0, r, range);
 }
@@ -273,7 +273,7 @@
 
 #if !defined(HAVE_BN_PSEUDO_RAND_RANGE)
 int
-BN_pseudo_rand_range(BIGNUM *r, BIGNUM *range)
+BN_pseudo_rand_range(BIGNUM *r, const BIGNUM *range)
 {
     return bn_rand_range(1, r, range);
 }
diff --git a/ext/openssl/openssl_missing.h b/ext/openssl/openssl_missing.h
--- a/ext/openssl/openssl_missing.h
+++ b/ext/openssl/openssl_missing.h
@@ -167,11 +167,11 @@
 #endif
 
 #if !defined(HAVE_BN_RAND_RANGE)
-int BN_rand_range(BIGNUM *r, BIGNUM *range);
+int BN_rand_range(BIGNUM *r, const BIGNUM *range);
 #endif
 
 #if !defined(HAVE_BN_PSEUDO_RAND_RANGE)
-int BN_pseudo_rand_range(BIGNUM *r, BIGNUM *range);
+int BN_pseudo_rand_range(BIGNUM *r, const BIGNUM *range);
 #endif
 
 #if !defined(HAVE_CONF_GET1_DEFAULT_CONFIG_FILE)