diff --git a/configure.in b/configure.in
index 498833ce1..78eea7f2c 100644
--- a/configure.in
+++ b/configure.in
@@ -505,11 +505,21 @@ AC_SUBST(GUILE_MAJOR_VERSION)
 AC_SUBST(GUILE_MINOR_VERSION)
 AC_SUBST(GUILE_VERSION)
 
+#######################################################################
+# library versioning
+
+AC_SUBST(LIBQTHREADS_INTERFACE_CURRENT)
+AC_SUBST(LIBQTHREADS_INTERFACE_REVISION)
+AC_SUBST(LIBQTHREADS_INTERFACE_AGE)
+AC_SUBST(LIBQTHREADS_INTERFACE)
+
 AC_SUBST(LIBGUILE_INTERFACE_CURRENT)
 AC_SUBST(LIBGUILE_INTERFACE_REVISION)
 AC_SUBST(LIBGUILE_INTERFACE_AGE)
 AC_SUBST(LIBGUILE_INTERFACE)
 
+#######################################################################
+
 dnl Tell guile-config what flags guile users should link against.
 GUILE_LIBS="$LDFLAGS $THREAD_LIBS_INSTALLED $LIBS"
 AC_SUBST(GUILE_LIBS)