diff --git a/configure/CONFIG_SITE b/configure/CONFIG_SITE
index 64fc0fd..7da9e08 100644
--- a/configure/CONFIG_SITE
+++ b/configure/CONFIG_SITE
@@ -28,3 +28,5 @@ USR_CPPFLAGS += --coverage
 USR_LDFLAGS += --coverage
 endif
 
+# shared library ABI version.
+SHRLIB_VERSION ?= 5.0