diff --git a/ext/openssl/extconf.rb b/ext/openssl/extconf.rb
index bd7c5770d..5cb28f309 100644
--- a/ext/openssl/extconf.rb
+++ b/ext/openssl/extconf.rb
@@ -130,9 +130,6 @@ def find_openssl_library
 if !have_struct_member("SSL", "ctx", "openssl/ssl.h") || is_libressl
   $defs.push("-DHAVE_OPAQUE_OPENSSL")
 end
-have_func("BN_GENCB_new")
-have_func("BN_GENCB_free")
-have_func("BN_GENCB_get_arg")
 have_func("EVP_MD_CTX_new")
 have_func("EVP_MD_CTX_free")
 have_func("EVP_MD_CTX_pkey_ctx")
diff --git a/ext/openssl/openssl_missing.h b/ext/openssl/openssl_missing.h
index 5586f9656..4d9b88013 100644
--- a/ext/openssl/openssl_missing.h
+++ b/ext/openssl/openssl_missing.h
@@ -13,18 +13,6 @@
 #include "ruby/config.h"
 
 /* added in 1.1.0 */
-#if !defined(HAVE_BN_GENCB_NEW)
-#  define BN_GENCB_new() ((BN_GENCB *)OPENSSL_malloc(sizeof(BN_GENCB)))
-#endif
-
-#if !defined(HAVE_BN_GENCB_FREE)
-#  define BN_GENCB_free(cb) OPENSSL_free(cb)
-#endif
-
-#if !defined(HAVE_BN_GENCB_GET_ARG)
-#  define BN_GENCB_get_arg(cb) (cb)->arg
-#endif
-
 #if !defined(HAVE_EVP_MD_CTX_NEW)
 #  define EVP_MD_CTX_new EVP_MD_CTX_create
 #endif
diff --git a/ext/openssl/ossl_pkey.c b/ext/openssl/ossl_pkey.c
index fce647d8f..40964e380 100644
--- a/ext/openssl/ossl_pkey.c
+++ b/ext/openssl/ossl_pkey.c
@@ -17,64 +17,6 @@ VALUE cPKey;
 VALUE ePKeyError;
 static ID id_private_q;
 
-/*
- * callback for generating keys
- */
-static VALUE
-call_check_ints0(VALUE arg)
-{
-    rb_thread_check_ints();
-    return Qnil;
-}
-
-static void *
-call_check_ints(void *arg)
-{
-    int state;
-    rb_protect(call_check_ints0, Qnil, &state);
-    return (void *)(VALUE)state;
-}
-
-int
-ossl_generate_cb_2(int p, int n, BN_GENCB *cb)
-{
-    VALUE ary;
-    struct ossl_generate_cb_arg *arg;
-    int state;
-
-    arg = (struct ossl_generate_cb_arg *)BN_GENCB_get_arg(cb);
-    if (arg->yield) {
-	ary = rb_ary_new2(2);
-	rb_ary_store(ary, 0, INT2NUM(p));
-	rb_ary_store(ary, 1, INT2NUM(n));
-
-	/*
-	* can be break by raising exception or 'break'
-	*/
-	rb_protect(rb_yield, ary, &state);
-	if (state) {
-	    arg->state = state;
-	    return 0;
-	}
-    }
-    if (arg->interrupted) {
-	arg->interrupted = 0;
-	state = (int)(VALUE)rb_thread_call_with_gvl(call_check_ints, NULL);
-	if (state) {
-	    arg->state = state;
-	    return 0;
-	}
-    }
-    return 1;
-}
-
-void
-ossl_generate_cb_stop(void *ptr)
-{
-    struct ossl_generate_cb_arg *arg = (struct ossl_generate_cb_arg *)ptr;
-    arg->interrupted = 1;
-}
-
 static void
 ossl_evp_pkey_free(void *ptr)
 {
@@ -247,6 +189,21 @@ pkey_gen_cb_yield(VALUE ctx_v)
     return rb_yield_values2(info_num, argv);
 }
 
+static VALUE
+call_check_ints0(VALUE arg)
+{
+    rb_thread_check_ints();
+    return Qnil;
+}
+
+static void *
+call_check_ints(void *arg)
+{
+    int state;
+    rb_protect(call_check_ints0, Qnil, &state);
+    return (void *)(VALUE)state;
+}
+
 static int
 pkey_gen_cb(EVP_PKEY_CTX *ctx)
 {
diff --git a/ext/openssl/ossl_pkey.h b/ext/openssl/ossl_pkey.h
index 7dbaed47b..629c16ae1 100644
--- a/ext/openssl/ossl_pkey.h
+++ b/ext/openssl/ossl_pkey.h
@@ -35,14 +35,6 @@ extern const rb_data_type_t ossl_evp_pkey_type;
     } \
 } while (0)
 
-struct ossl_generate_cb_arg {
-    int yield;
-    int interrupted;
-    int state;
-};
-int ossl_generate_cb_2(int p, int n, BN_GENCB *cb);
-void ossl_generate_cb_stop(void *ptr);
-
 VALUE ossl_pkey_new(EVP_PKEY *);
 void ossl_pkey_check_public_key(const EVP_PKEY *);
 EVP_PKEY *ossl_pkey_read_generic(BIO *, VALUE);