diff --git a/src/mathed/MathData.cpp b/src/mathed/MathData.cpp
index 4c33934828..38f44a696e 100644
--- a/src/mathed/MathData.cpp
+++ b/src/mathed/MathData.cpp
@@ -49,7 +49,9 @@ namespace lyx {
 
 MathData::MathData(Buffer * buf, const_iterator from, const_iterator to)
 	: base_type(from, to), buffer_(buf)
-{}
+{
+	setContentsBuffer();
+}
 
 
 void MathData::setContentsBuffer()
diff --git a/status.24x b/status.24x
index 0328af480b..e7f677295e 100644
--- a/status.24x
+++ b/status.24x
@@ -90,6 +90,8 @@ What's new
 
 - Fix initialization of an internal value.
 
+- Fix "Unassigned buffer_" error with math references (bug 12947).
+
 
 * DOCUMENTATION AND LOCALIZATION