diff --git a/CMakeLists.txt b/CMakeLists.txt
index ecb90a23..a5061e03 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -63,6 +63,9 @@ find_package(Libcares 1.7.5)
 find_package(ZLIB 1.2.3)
 find_package(Libngtcp2 0.0.0)
 find_package(Libngtcp2_crypto_openssl 0.0.0)
+if(LIBNGTCP2_CRYPTO_OPENSSL_FOUND)
+  set(HAVE_LIBNGTCP2_CRYPTO_OPENSSL 1)
+endif()
 find_package(Libnghttp3 0.0.0)
 find_package(Libbpf 0.4.0)
 if(OPENSSL_FOUND AND LIBEV_FOUND AND ZLIB_FOUND)
diff --git a/cmakeconfig.h.in b/cmakeconfig.h.in
index 10bb76cb..2e357d53 100644
--- a/cmakeconfig.h.in
+++ b/cmakeconfig.h.in
@@ -87,3 +87,6 @@
 
 /* Define to 1 if you have enum bpf_stats_type in linux/bpf.h. */
 #cmakedefine HAVE_BPF_STATS_TYPE 1
+
+/* Define to 1 if you have `libngtcp2_crypto_openssl` library. */
+#cmakedefine HAVE_LIBNGTCP2_CRYPTO_OPENSSL