diff --git a/CMakeLists.txt b/CMakeLists.txt
index b8e50916..a535727e 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -117,6 +117,7 @@ if ((NOT ENABLE_SHARED) AND (NOT ENABLE_STATIC))
 endif ()
 
 set(DNSSEC_ROADBLOCK_AVOIDANCE ON CACHE BOOL "Enable/disable DNSSEC roadblock avoidance.")
+set(FD_SETSIZE "" CACHE STRING "Set maximum file descriptor number that can be used by select.")
 set(MAX_UDP_BACKOFF 1000 CACHE STRING "Set the maximum number of messages that can be sent to other upstreams before the upstream which has previously timed out will be tried again.")
 set(STUB_NATIVE_DNSSEC ON CACHE BOOL "Enable/disable native stub DNSSEC support.")
 
diff --git a/cmake/include/cmakeconfig.h.in b/cmake/include/cmakeconfig.h.in
index af5a611a..e5463207 100644
--- a/cmake/include/cmakeconfig.h.in
+++ b/cmake/include/cmakeconfig.h.in
@@ -164,6 +164,8 @@
 
 #cmakedefine STRPTIME_WORKS		1
 
+#cmakedefine FD_SETSIZE			@FD_SETSIZE@
+
 #cmakedefine HAVE_TARGET_ENDIANNESS
 #cmakedefine TARGET_IS_BIG_ENDIAN