diff --git a/external/unbound/configure_checks.cmake b/external/unbound/configure_checks.cmake
index edb64c78..1cfc20d3 100644
--- a/external/unbound/configure_checks.cmake
+++ b/external/unbound/configure_checks.cmake
@@ -58,7 +58,6 @@ check_function_exists(ctime_r HAVE_CTIME_R)
 check_function_exists(daemon HAVE_DAEMON)
 check_function_exists(endprotoent HAVE_ENDPROTOENT)
 check_function_exists(endservent HAVE_ENDSERVENT)
-check_function_exists(fnctl HAVE_FNCTL)
 check_function_exists(fork HAVE_FORK)
 check_function_exists(fseeko HAVE_FSEEKO)
 check_function_exists(fsync HAVE_FSYNC)