diff --git a/configure.ac b/configure.ac
index d21ebfe52..5cf1e080e 100644
--- a/configure.ac
+++ b/configure.ac
@@ -20,6 +20,9 @@ LIBXML_MICRO_VERSION_SUFFIX=
 LIBXML_MINOR_COMPAT=14
 LIBXML_CURRENT=`expr $LIBXML_MAJOR_VERSION + $LIBXML_MINOR_VERSION`
 LIBXML_AGE=`expr $LIBXML_MINOR_VERSION - $LIBXML_MINOR_COMPAT`
+# At least on Linux, libtool will set SOVERSION to (CURRENT - AGE)
+# which equals (MAJOR + MINOR_COMPAT). The other build systems must
+# emulate this behavior.
 LIBXML_VERSION_INFO=$LIBXML_CURRENT:$LIBXML_MICRO_VERSION:$LIBXML_AGE
 
 LIBXML_VERSION_NUMBER=`expr $LIBXML_MAJOR_VERSION \* 10000 + $LIBXML_MINOR_VERSION \* 100 + $LIBXML_MICRO_VERSION`