diff --git a/ext/openssl/ossl.c b/ext/openssl/ossl.c
index 27d7f9cfdf..60780790b0 100644
--- a/ext/openssl/ossl.c
+++ b/ext/openssl/ossl.c
@@ -69,16 +69,9 @@ ossl_##name##_sk2ary(const STACK_OF(type) *sk)	\
     int i, num;					\
     VALUE ary;					\
 						\
-    if (!sk) {					\
-	OSSL_Debug("empty sk!");		\
-	return Qnil;				\
-    }						\
+    RUBY_ASSERT(sk != NULL);			\
     num = sk_##type##_num(sk);			\
-    if (num < 0) {				\
-	OSSL_Debug("items in sk < -1???");	\
-	return rb_ary_new();			\
-    }						\
-    ary = rb_ary_new2(num);			\
+    ary = rb_ary_new_capa(num);			\
 						\
     for (i=0; i<num; i++) {			\
 	t = sk_##type##_value(sk, i);		\
diff --git a/ext/openssl/ossl_pkcs7.c b/ext/openssl/ossl_pkcs7.c
index e502c9542f..94eb22aa82 100644
--- a/ext/openssl/ossl_pkcs7.c
+++ b/ext/openssl/ossl_pkcs7.c
@@ -557,21 +557,16 @@ ossl_pkcs7_get_signer(VALUE self)
 {
     PKCS7 *pkcs7;
     STACK_OF(PKCS7_SIGNER_INFO) *sk;
-    PKCS7_SIGNER_INFO *si;
     int num, i;
     VALUE ary;
 
     GetPKCS7(self, pkcs7);
-    if (!(sk = PKCS7_get_signer_info(pkcs7))) {
-	OSSL_Debug("OpenSSL::PKCS7#get_signer_info == NULL!");
-	return rb_ary_new();
-    }
-    if ((num = sk_PKCS7_SIGNER_INFO_num(sk)) < 0) {
-	ossl_raise(ePKCS7Error, "Negative number of signers!");
-    }
-    ary = rb_ary_new2(num);
+    if (!(sk = PKCS7_get_signer_info(pkcs7)))
+        return rb_ary_new();
+    num = sk_PKCS7_SIGNER_INFO_num(sk);
+    ary = rb_ary_new_capa(num);
     for (i=0; i<num; i++) {
-	si = sk_PKCS7_SIGNER_INFO_value(sk, i);
+	PKCS7_SIGNER_INFO *si = sk_PKCS7_SIGNER_INFO_value(sk, i);
 	rb_ary_push(ary, ossl_pkcs7si_new(si));
     }
 
@@ -604,7 +599,6 @@ ossl_pkcs7_get_recipient(VALUE self)
 {
     PKCS7 *pkcs7;
     STACK_OF(PKCS7_RECIP_INFO) *sk;
-    PKCS7_RECIP_INFO *si;
     int num, i;
     VALUE ary;
 
@@ -615,13 +609,11 @@ ossl_pkcs7_get_recipient(VALUE self)
 	sk = pkcs7->d.signed_and_enveloped->recipientinfo;
     else sk = NULL;
     if (!sk) return rb_ary_new();
-    if ((num = sk_PKCS7_RECIP_INFO_num(sk)) < 0) {
-	ossl_raise(ePKCS7Error, "Negative number of recipient!");
-    }
-    ary = rb_ary_new2(num);
+    num = sk_PKCS7_RECIP_INFO_num(sk);
+    ary = rb_ary_new_capa(num);
     for (i=0; i<num; i++) {
-	si = sk_PKCS7_RECIP_INFO_value(sk, i);
-	rb_ary_push(ary, ossl_pkcs7ri_new(si));
+        PKCS7_RECIP_INFO *ri = sk_PKCS7_RECIP_INFO_value(sk, i);
+        rb_ary_push(ary, ossl_pkcs7ri_new(ri));
     }
 
     return ary;
@@ -701,7 +693,10 @@ ossl_pkcs7_set_certificates(VALUE self, VALUE ary)
     X509 *cert;
 
     certs = pkcs7_get_certs(self);
-    while((cert = sk_X509_pop(certs))) X509_free(cert);
+    if (certs) {
+        while ((cert = sk_X509_pop(certs)))
+            X509_free(cert);
+    }
     rb_block_call(ary, rb_intern("each"), 0, 0, ossl_pkcs7_set_certs_i, self);
 
     return ary;
@@ -710,7 +705,10 @@ ossl_pkcs7_set_certificates(VALUE self, VALUE ary)
 static VALUE
 ossl_pkcs7_get_certificates(VALUE self)
 {
-    return ossl_x509_sk2ary(pkcs7_get_certs(self));
+    STACK_OF(X509) *certs = pkcs7_get_certs(self);
+    if (!certs)
+        return Qnil;
+    return ossl_x509_sk2ary(certs);
 }
 
 static VALUE
@@ -741,7 +739,10 @@ ossl_pkcs7_set_crls(VALUE self, VALUE ary)
     X509_CRL *crl;
 
     crls = pkcs7_get_crls(self);
-    while((crl = sk_X509_CRL_pop(crls))) X509_CRL_free(crl);
+    if (crls) {
+        while ((crl = sk_X509_CRL_pop(crls)))
+            X509_CRL_free(crl);
+    }
     rb_block_call(ary, rb_intern("each"), 0, 0, ossl_pkcs7_set_crls_i, self);
 
     return ary;
@@ -750,7 +751,10 @@ ossl_pkcs7_set_crls(VALUE self, VALUE ary)
 static VALUE
 ossl_pkcs7_get_crls(VALUE self)
 {
-    return ossl_x509crl_sk2ary(pkcs7_get_crls(self));
+    STACK_OF(X509_CRL) *crls = pkcs7_get_crls(self);
+    if (!crls)
+        return Qnil;
+    return ossl_x509crl_sk2ary(crls);
 }
 
 static VALUE
diff --git a/ext/openssl/ossl_ssl.c b/ext/openssl/ossl_ssl.c
index b9033d4d0e..db44c423f2 100644
--- a/ext/openssl/ossl_ssl.c
+++ b/ext/openssl/ossl_ssl.c
@@ -2450,7 +2450,7 @@ ossl_ssl_get_peer_finished(VALUE self)
 
 /*
  * call-seq:
- *    ssl.client_ca => [x509name, ...]
+ *    ssl.client_ca => [x509name, ...] or nil
  *
  * Returns the list of client CAs. Please note that in contrast to
  * SSLContext#client_ca= no array of X509::Certificate is returned but
@@ -2468,6 +2468,8 @@ ossl_ssl_get_client_ca_list(VALUE self)
     GetSSL(self, ssl);
 
     ca = SSL_get_client_CA_list(ssl);
+    if (!ca)
+        return Qnil;
     return ossl_x509name_sk2ary(ca);
 }
 
diff --git a/ext/openssl/ossl_x509crl.c b/ext/openssl/ossl_x509crl.c
index 644d70a581..cfaf39640b 100644
--- a/ext/openssl/ossl_x509crl.c
+++ b/ext/openssl/ossl_x509crl.c
@@ -276,21 +276,19 @@ ossl_x509crl_get_revoked(VALUE self)
 {
     X509_CRL *crl;
     int i, num;
-    X509_REVOKED *rev;
-    VALUE ary, revoked;
+    STACK_OF(X509_REVOKED) *sk;
+    VALUE ary;
 
     GetX509CRL(self, crl);
-    num = sk_X509_REVOKED_num(X509_CRL_get_REVOKED(crl));
-    if (num < 0) {
-	OSSL_Debug("num < 0???");
-	return rb_ary_new();
-    }
-    ary = rb_ary_new2(num);
+    sk = X509_CRL_get_REVOKED(crl);
+    if (!sk)
+        return rb_ary_new();
+
+    num = sk_X509_REVOKED_num(sk);
+    ary = rb_ary_new_capa(num);
     for(i=0; i<num; i++) {
-	/* NO DUP - don't free! */
-	rev = sk_X509_REVOKED_value(X509_CRL_get_REVOKED(crl), i);
-	revoked = ossl_x509revoked_new(rev);
-	rb_ary_push(ary, revoked);
+	X509_REVOKED *rev = sk_X509_REVOKED_value(sk, i);
+	rb_ary_push(ary, ossl_x509revoked_new(rev));
     }
 
     return ary;