diff --git a/configure.ac b/configure.ac
index e05db660..eec8c1a5 100644
--- a/configure.ac
+++ b/configure.ac
@@ -305,33 +305,36 @@ AC_SEARCH_LIBS([dlopen], [dl], [],
 
 # ----- Check for pthreads
 
+AX_PTHREAD([
+	AC_DEFINE([HAVE_PTHREAD], [1], [Define if you have POSIX threads libraries and header files.])
+	appendCXX "$PTHREAD_CFLAGS"
+	appendLib "$PTHREAD_LIBS"
+], [
+	AC_MSG_ERROR([This compiler/OS doesn't seem to support pthreads.])
+])
+
+# Note that old broken systems, such as OpenBSD, NetBSD, which don't support AI_ADDRCONFIG, also have thread-unsafe getaddrinfo().
+# Gladly, they fixed thread-safety before support of AI_ADDRCONFIG, so this can be abused to detect the thread-safe getaddrinfo().
+#
+# TODO: drop support of blocking DNS at some point. OpenBSD supports AI_ADDRCONFIG since Nov 2014, and their getaddrinfo() is thread-safe since Nov 2013. NetBSD's one is thread-safe since ages ago.
 DNS_TEXT=blocking
 if test "x$TDNS" != "xno"; then
 	old_TDNS=$TDNS
-	AX_PTHREAD([
-        	AC_DEFINE([HAVE_PTHREAD], [1], [Define if you have POSIX threads libraries and header files.])
-		appendCXX "$PTHREAD_CFLAGS"
-		appendLib "$PTHREAD_LIBS"
-		AC_MSG_CHECKING([whether getaddrinfo() supports AI_ADDRCONFIG])
-		AC_COMPILE_IFELSE([
-			AC_LANG_PROGRAM([[
-				#include <sys/types.h>
-				#include <sys/socket.h>
-				#include <netdb.h>
-			]], [[
-				int x = AI_ADDRCONFIG;
-				(void) x;
-			]])
-		], [
-			AC_MSG_RESULT([yes])
-			TDNS=yes
-		], [
-			AC_MSG_RESULT([no])
-			TDNS=no
-			# Note that broken systems, such as OpenBSD, NetBSD, which don't support AI_ADDRCONFIG,
-			# also have thread-unsafe getaddrinfo().
-		])
+	AC_MSG_CHECKING([whether getaddrinfo() supports AI_ADDRCONFIG])
+	AC_COMPILE_IFELSE([
+		AC_LANG_PROGRAM([[
+			#include <sys/types.h>
+			#include <sys/socket.h>
+			#include <netdb.h>
+		]], [[
+			int x = AI_ADDRCONFIG;
+			(void) x;
+		]])
 	], [
+		AC_MSG_RESULT([yes])
+		TDNS=yes
+	], [
+		AC_MSG_RESULT([no])
 		TDNS=no
 	])
 	if test "x$TDNS" = "xyes"; then
diff --git a/include/znc/Socket.h b/include/znc/Socket.h
index df091f03..1c82b3a7 100644
--- a/include/znc/Socket.h
+++ b/include/znc/Socket.h
@@ -135,8 +135,10 @@ public:
 private:
 	void FinishConnect(const CString& sHostname, u_short iPort, const CString& sSockName, int iTimeout, bool bSSL, const CString& sBindHost, CZNCSock *pcSock);
 
-	class CTDNSMonitorFD;
-	friend class CTDNSMonitorFD;
+#ifdef HAVE_PTHREAD
+	class CThreadMonitorFD;
+	friend class CThreadMonitorFD;
+#endif
 #ifdef HAVE_THREADED_DNS
 	struct TDNSTask {
 		TDNSTask() : sHostname(""), iPort(0), sSockName(""), iTimeout(0), bSSL(false), sBindhost(""), pcSock(nullptr), bDoneTarget(false), bDoneBind(false), aiTarget(nullptr), aiBind(nullptr) {}
diff --git a/src/Socket.cpp b/src/Socket.cpp
index 2787caa9..d316bcdc 100644
--- a/src/Socket.cpp
+++ b/src/Socket.cpp
@@ -158,9 +158,9 @@ CString CZNCSock::GetSSLPeerFingerprint() const {
 }
 
 #ifdef HAVE_PTHREAD
-class CSockManager::CTDNSMonitorFD : public CSMonitorFD {
+class CSockManager::CThreadMonitorFD : public CSMonitorFD {
 public:
-	CTDNSMonitorFD() {
+	CThreadMonitorFD() {
 		Add(CThreadPool::Get().getReadFD(), ECT_Read);
 	}
 
@@ -346,7 +346,7 @@ void CSockManager::SetTDNSThreadFinished(TDNSTask* task, bool bBind, addrinfo* a
 
 CSockManager::CSockManager() {
 #ifdef HAVE_PTHREAD
-	MonitorFD(new CTDNSMonitorFD());
+	MonitorFD(new CThreadMonitorFD());
 #endif
 }