diff --git a/src/ChangeLog b/src/ChangeLog
index 0b60ab4ff0..69d2844669 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,7 @@
+2004-11-09  Jean-Marc Lasgouttes  <lasgouttes@lyx.org>
+
+	* lengthcommon.C (unitFromString): fix off-by-one error (bug 1682)
+
 2004-11-05  Jean-Marc Lasgouttes  <lasgouttes@lyx.org>
 
 	* lyxfunc.C (dispatch): remove the verbose argument
diff --git a/src/lengthcommon.C b/src/lengthcommon.C
index 89ff7e1a55..ffb01bc566 100644
--- a/src/lengthcommon.C
+++ b/src/lengthcommon.C
@@ -61,7 +61,7 @@ char const * const unit_name_gui[] = {
 LyXLength::UNIT unitFromString(string const & data)
 {
 	int i = 0;
-	while (i < num_units && data != unit_name[i])
+	while (i < num_units - 1 && data != unit_name[i])
 		++i;
 	return static_cast<LyXLength::UNIT>(i);
 }