diff --git a/CMakeLists.txt b/CMakeLists.txt
index 00ed2bd81..a30ded9d3 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1762,8 +1762,8 @@ CHECK_FUNCTION_EXISTS(SSL_get0_alpn_selected LWS_HAVE_SSL_get0_alpn_selected)
 CHECK_FUNCTION_EXISTS(SSL_set_alpn_protos LWS_HAVE_SSL_set_alpn_protos)
 CHECK_FUNCTION_EXISTS(SSL_CTX_set_ciphersuites LWS_HAVE_SSL_CTX_set_ciphersuites)
 if (LWS_WITH_SSL AND NOT LWS_WITH_MBEDTLS)
-CHECK_SYMBOL_EXISTS(SSL_CTX_get_extra_chain_certs_only openssl/ssl.h LWS_HAVE_SSL_EXTRA_CHAIN_CERTS)
-CHECK_FUNCTION_EXISTS(EVP_MD_CTX_free LWS_HAVE_EVP_MD_CTX_free)
+CHECK_C_SOURCE_COMPILES("#include <openssl/ssl.h>\nint main(void) { STACK_OF(X509) *c = NULL; SSL_CTX *ctx = NULL; return (int)SSL_CTX_get_extra_chain_certs_only(ctx, &c); }\n" LWS_HAVE_SSL_EXTRA_CHAIN_CERTS)
+CHECK_C_SOURCE_COMPILES("#include <openssl/ssl.h>\nint main(void) { EVP_MD_CTX *md_ctx = NULL; EVP_MD_CTX_free(md_ctx); return 0; }\n" LWS_HAVE_EVP_MD_CTX_free)
 CHECK_FUNCTION_EXISTS(ECDSA_SIG_set0 LWS_HAVE_ECDSA_SIG_set0)
 CHECK_FUNCTION_EXISTS(BN_bn2binpad LWS_HAVE_BN_bn2binpad)
 CHECK_FUNCTION_EXISTS(EVP_aes_128_wrap LWS_HAVE_EVP_aes_128_wrap)