diff --git a/configure b/configure
index 9df1bc28a..4575fcf35 100755
--- a/configure
+++ b/configure
@@ -6380,7 +6380,6 @@ else
   # link with -lpcap for the purposes of this test
   LIBS_OLD="$LIBS"
   LIBS="$LIBS -lpcap"
-  PCAP_DEFINE_NETMASK_UNKNOWN
   for ac_func in pcap_set_immediate_mode
 do :
   ac_fn_c_check_func "$LINENO" "pcap_set_immediate_mode" "ac_cv_func_pcap_set_immediate_mode"
diff --git a/configure.ac b/configure.ac
index 013b52f0f..be96ccd9c 100644
--- a/configure.ac
+++ b/configure.ac
@@ -485,7 +485,6 @@ else
   # link with -lpcap for the purposes of this test
   LIBS_OLD="$LIBS"
   LIBS="$LIBS -lpcap"
-  PCAP_DEFINE_NETMASK_UNKNOWN
   AC_CHECK_FUNCS([pcap_set_immediate_mode])
   # Restore libs
   LIBS="$LIBS_OLD"
diff --git a/nsock/src/configure b/nsock/src/configure
index 55c812261..9be2e6a5e 100755
--- a/nsock/src/configure
+++ b/nsock/src/configure
@@ -3672,8 +3672,6 @@ $as_echo "#define HAVE_PCAP 1" >>confdefs.h
 fi
 
 
-PCAP_DEFINE_NETMASK_UNKNOWN
-
   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 86106c1e6..09dfb0849 100644
--- a/nsock/src/configure.ac
+++ b/nsock/src/configure.ac
@@ -180,8 +180,6 @@ if test "$have_libpcap" != "no"; then
 fi
 AC_SUBST(LIBPCAP_LIBS)
 
-PCAP_DEFINE_NETMASK_UNKNOWN
-
 AX_HAVE_EPOLL([AC_DEFINE(HAVE_EPOLL, 1, [epoll is available])], )
 AX_HAVE_POLL([AC_DEFINE(HAVE_POLL, 1, [poll is available])], )
 AC_CHECK_FUNCS(kqueue kevent, [AC_DEFINE(HAVE_KQUEUE)], )