diff --git a/src/libpttls/Makefile.am b/src/libpttls/Makefile.am
index f2bcf44d5..7e67600ca 100644
--- a/src/libpttls/Makefile.am
+++ b/src/libpttls/Makefile.am
@@ -13,6 +13,10 @@ libpttls_la_LIBADD = \
 	$(top_builddir)/src/libstrongswan/libstrongswan.la \
 	$(top_builddir)/src/libtls/libtls.la
 
+if USE_WINDOWS
+  libpttls_la_LIBADD += -lws2_32
+endif
+
 libpttls_la_SOURCES = pt_tls.c pt_tls.h \
 	pt_tls_client.c pt_tls_client.h \
 	pt_tls_server.c pt_tls_server.h \