diff --git a/nsock/include/nsock_config.h.in b/nsock/include/nsock_config.h.in
index 8279c2924..4bc334f11 100644
--- a/nsock/include/nsock_config.h.in
+++ b/nsock/include/nsock_config.h.in
@@ -85,3 +85,5 @@
 #undef HAVE_EPOLL
 #undef HAVE_POLL
 #undef HAVE_KQUEUE
+
+#undef PCAP_NETMASK_UNKNOWN
diff --git a/nsock/include/nsock_winconfig.h b/nsock/include/nsock_winconfig.h
index 5d77527cb..0f281c8cb 100644
--- a/nsock/include/nsock_winconfig.h
+++ b/nsock/include/nsock_winconfig.h
@@ -95,6 +95,8 @@
 
 #ifndef DISABLE_NSOCK_PCAP
 #define HAVE_PCAP 1
+/* WinPCAP doesn't have this */
+#define PCAP_NETMASK_UNKNOWN 0
 #endif
 
  /* WSAPoll() isn't available before Vista */
diff --git a/nsock/src/acinclude.m4 b/nsock/src/acinclude.m4
index 9a972cc97..696cd3414 100644
--- a/nsock/src/acinclude.m4
+++ b/nsock/src/acinclude.m4
@@ -118,3 +118,24 @@ $1],[AC_MSG_RESULT([no])
 $2])
 ])dnl
 
+dnl Checks if PCAP_NETMASK_UNKNOWN is defined (has been since libpcap 1.1.1)
+dnl Sets it to 0 (no checking) if it's not defined.
+AC_DEFUN([PCAP_DEFINE_NETMASK_UNKNOWN],
+[
+  AC_MSG_CHECKING(if PCAP_NETMASK_UNKNOWN is defined/handled by libpcap)
+  AC_CACHE_VAL(ac_cv_have_pcap_netmask_unknown,
+    AC_TRY_COMPILE(
+      [
+      #include <pcap.h>
+      ],
+      [
+      int i = PCAP_NETMASK_UNKNOWN;
+      ],
+      ac_cv_have_pcap_netmask_unknown=yes,
+      ac_cv_have_pcap_netmask_unknown=no))
+  if test $ac_cv_have_pcap_netmask_unknown = no; then
+    AC_DEFINE(PCAP_NETMASK_UNKNOWN, 0, [Possibly using libpcap prior to 1.1.0.])
+  fi
+  AC_MSG_RESULT($ac_cv_have_pcap_netmask_unknown)
+])
+
diff --git a/nsock/src/configure b/nsock/src/configure
index f0d3cd22c..8e811ded8 100755
--- a/nsock/src/configure
+++ b/nsock/src/configure
@@ -3625,6 +3625,44 @@ if test "$have_libpcap" != "no"; then
 fi
 
 
+
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking if PCAP_NETMASK_UNKNOWN is defined/handled by libpcap" >&5
+$as_echo_n "checking if PCAP_NETMASK_UNKNOWN is defined/handled by libpcap... " >&6; }
+  if ${ac_cv_have_pcap_netmask_unknown+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+      #include <pcap.h>
+
+int
+main ()
+{
+
+      int i = PCAP_NETMASK_UNKNOWN;
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  ac_cv_have_pcap_netmask_unknown=yes
+else
+  ac_cv_have_pcap_netmask_unknown=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+fi
+
+  if test $ac_cv_have_pcap_netmask_unknown = no; then
+
+$as_echo "#define PCAP_NETMASK_UNKNOWN 0" >>confdefs.h
+
+  fi
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_have_pcap_netmask_unknown" >&5
+$as_echo "$ac_cv_have_pcap_netmask_unknown" >&6; }
+
+
   ax_have_epoll_cppflags="${CPPFLAGS}"
   ac_fn_c_check_header_mongrel "$LINENO" "linux/version.h" "ac_cv_header_linux_version_h" "$ac_includes_default"
 if test "x$ac_cv_header_linux_version_h" = xyes; then :
diff --git a/nsock/src/configure.ac b/nsock/src/configure.ac
index 1772e9da8..2a0ba2034 100644
--- a/nsock/src/configure.ac
+++ b/nsock/src/configure.ac
@@ -168,6 +168,8 @@ if test "$have_libpcap" != "no"; then
 fi
 AC_SUBST(LIBPCAP_LIBS)
 
+PCAP_DEFINE_NETMASK_UNKNOWN
+
 AX_HAVE_EPOLL([AC_DEFINE(HAVE_EPOLL)], )
 AX_HAVE_POLL([AC_DEFINE(HAVE_POLL)], )
 AC_CHECK_FUNCS(kqueue kevent, [AC_DEFINE(HAVE_KQUEUE)], )
diff --git a/nsock/src/error.h b/nsock/src/error.h
index c00088759..60a97bbff 100644
--- a/nsock/src/error.h
+++ b/nsock/src/error.h
@@ -74,13 +74,18 @@
 #include <unistd.h>
 #endif
 
+#if defined(__GNUC__)
+#define NORETURN __attribute__((noreturn))
+#elif defined(_MSC_VER)
+#define NORETURN __declspec((noreturn))
+#else
+#define NORETURN
+#endif
 
-void fatal(char *fmt, ...)
-  __attribute__ ((noreturn))
+NORETURN void fatal(char *fmt, ...)
   __attribute__ ((format (printf, 1, 2)));
 
-void pfatal(char *fmt, ...)
-  __attribute__ ((noreturn))
+NORETURN void pfatal(char *fmt, ...)
   __attribute__ ((format (printf, 1, 2)));
 
 #endif /* ERROR_H */
diff --git a/nsock/src/nsock_pcap.c b/nsock/src/nsock_pcap.c
index aa977a5f9..04980cb18 100644
--- a/nsock/src/nsock_pcap.c
+++ b/nsock/src/nsock_pcap.c
@@ -107,7 +107,7 @@ static int nsock_pcap_set_filter(struct npool *nsp, pcap_t *pt, const char *devi
   struct bpf_program fcode;
   int rc;
 
-  rc = pcap_compile(pt, &fcode, (char *)bpf, 1, 0);
+  rc = pcap_compile(pt, &fcode, (char *)bpf, 1, PCAP_NETMASK_UNKNOWN);
   if (rc) {
     nsock_log_error(nsp, "Error compiling pcap filter: %s", pcap_geterr(pt));
     return rc;
diff --git a/nsock/src/nsock_proxy.c b/nsock/src/nsock_proxy.c
index 71891db37..1ede70219 100644
--- a/nsock/src/nsock_proxy.c
+++ b/nsock/src/nsock_proxy.c
@@ -375,6 +375,7 @@ static struct proxy_node *proxy_node_new(char *proxystr) {
     }
   }
   fatal("Invalid protocol in proxy specification string: %s", proxystr);
+  return NULL;
 }
 
 struct proxy_parser *proxy_parser_new(const char *proxychainstr) {
diff --git a/nsock/tests/connect.c b/nsock/tests/connect.c
index 0baf602db..e4027bf38 100644
--- a/nsock/tests/connect.c
+++ b/nsock/tests/connect.c
@@ -93,7 +93,7 @@ static int connect_tcp_failure(void *tdata) {
                     (struct sockaddr *)&peer, 0, PORT_TCP);
 
   nsock_loop(ctd->nsp, 4000);
-  AssertEqual(ctd->connect_result, -EINVAL);
+  AssertEqual(ctd->connect_result, EINVAL);
   return 0;
 }