diff --git a/ast.news b/ast.news
index dcb2445a..cbefd459 100644
--- a/ast.news
+++ b/ast.news
@@ -25,6 +25,13 @@ the SipOK attribute of the FitsChan is set to a non-zero value (which is
 the default), and the FrameSet being written out contains an appropriate
 PolyMap that conforms to the requirements of the SIP convention.
 
+- The behaviour of the astLinearApprox method of the Mapping class has
+been changed in cases where the Mapping being approximated generates bad
+(AST__BAD) values for one or more of its outputs. Previously, any such
+Mapping would be deemed non-linear and no fit would be returned. Now, a
+fit is returned, provided the other outputs of the Mapping are linear,
+but the fit contains AST__BAD values for the coefficients describing the
+bad Mapping output.
 
 
 Main Changes in V8.6.1
diff --git a/sun_master.tex b/sun_master.tex
index 91b55744..cfa6c431 100644
--- a/sun_master.tex
+++ b/sun_master.tex
@@ -21843,6 +21843,14 @@ \subsection{\xlabel{changes}\xlabel{list_of_most_recent_changes}Changes
 
 \begin{enumerate}
 
+\item The behaviour of the astLinearApprox method of the Mapping class has
+been changed in cases where the Mapping being approximated generates bad
+(AST\_\_BAD) values for one or more of its outputs. Previously, any such
+Mapping would be deemed non-linear and no fit would be returned. Now, a
+fit is returned, provided the other outputs of the Mapping are linear,
+but the fit contains AST\_\_BAD values for the coefficients describing the
+bad Mapping output.
+
 \item The astWrite method of the FitsChan class can now create FITS-WCS headers
 that include keyords describing focal plane distortion using the
 conventions of the Spitzer SIP scheme. This is however only possible if