diff --git a/hs20/client/est.c b/hs20/client/est.c
index b1aacb8ff..db65334b2 100644
--- a/hs20/client/est.c
+++ b/hs20/client/est.c
@@ -16,6 +16,7 @@
 #include <openssl/asn1t.h>
 #include <openssl/x509.h>
 #include <openssl/x509v3.h>
+#include <openssl/opensslv.h>
 #ifdef OPENSSL_IS_BORINGSSL
 #include <openssl/buf.h>
 #endif /* OPENSSL_IS_BORINGSSL */
@@ -219,6 +220,10 @@ typedef struct {
 	} d;
 } AttrOrOID;
 
+#if OPENSSL_VERSION_NUMBER >= 0x10100000L && !defined(OPENSSL_IS_BORINGSSL)
+DEFINE_STACK_OF(AttrOrOID)
+#endif
+
 typedef struct {
 	int type;
 	STACK_OF(AttrOrOID) *attrs;
@@ -352,9 +357,17 @@ static void add_csrattrs(struct hs20_osu_client *ctx, CsrAttrs *csrattrs,
 		}
 	}
 #else /* OPENSSL_IS_BORINGSSL */
+#if OPENSSL_VERSION_NUMBER >= 0x10100000L && !defined(OPENSSL_IS_BORINGSSL)
+	num = sk_AttrOrOID_num(csrattrs->attrs);
+#else
 	num = SKM_sk_num(AttrOrOID, csrattrs->attrs);
+#endif
 	for (i = 0; i < num; i++) {
+#if OPENSSL_VERSION_NUMBER >= 0x10100000L && !defined(OPENSSL_IS_BORINGSSL)
+		AttrOrOID *ao = sk_AttrOrOID_value(csrattrs->attrs, i);
+#else
 		AttrOrOID *ao = SKM_sk_value(AttrOrOID, csrattrs->attrs, i);
+#endif
 		switch (ao->type) {
 		case 0:
 			add_csrattrs_oid(ctx, ao->d.oid, exts);