change library interface version
diff --git a/Makefile.am b/Makefile.am
index 8075823..e9a0039 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -6,6 +6,7 @@
 
 lib_LTLIBRARIES = libtelnet.la
 libtelnet_la_SOURCES = libtelnet.c libtelnet.h
+libtelnet_la_LDFLAGS = -version-info 1:0:0
 
 bin_PROGRAMS = telnet-client telnet-chatd telnet-proxy