diff --git a/src/resolve/resolved-dnstls-openssl.c b/src/resolve/resolved-dnstls-openssl.c
index bdd37a637f..ccd35671eb 100644
--- a/src/resolve/resolved-dnstls-openssl.c
+++ b/src/resolve/resolved-dnstls-openssl.c
@@ -10,6 +10,8 @@
 #include "resolved-dns-stream.h"
 #include "resolved-dnstls.h"
 
+#include "io-util.h"
+
 DEFINE_TRIVIAL_CLEANUP_FUNC(SSL*, SSL_free);
 DEFINE_TRIVIAL_CLEANUP_FUNC(BIO*, BIO_free);