diff --git a/collects/mred/private/kernel.ss b/collects/mred/private/kernel.ss
index e21bfd92..f448c678 100644
--- a/collects/mred/private/kernel.ss
+++ b/collects/mred/private/kernel.ss
@@ -240,6 +240,7 @@
     can-save-file?
     on-new-box
     on-new-image-snip
+    size-cache-invalid
     invalidate-bitmap-cache
     on-paint
     write-footers-to-file
@@ -921,6 +922,7 @@
     can-save-file?
     on-new-box
     on-new-image-snip
+    size-cache-invalid
     invalidate-bitmap-cache
     on-paint
     write-footers-to-file
@@ -1133,6 +1135,7 @@
     can-save-file?
     on-new-box
     on-new-image-snip
+    size-cache-invalid
     invalidate-bitmap-cache
     on-paint
     write-footers-to-file
diff --git a/collects/scribblings/gui/editor-intf.scrbl b/collects/scribblings/gui/editor-intf.scrbl
index 3b4cff2d..0b4e7714 100644
--- a/collects/scribblings/gui/editor-intf.scrbl
+++ b/collects/scribblings/gui/editor-intf.scrbl
@@ -1015,7 +1015,7 @@ The default implementation triggers a redraw of the editor, either
  immediately or at the end of the current edit sequence (if any)
  started by @method[editor<%> begin-edit-sequence].
 
-}
+See also @method[editor<%> size-cache-invalid].}
 
 
 @defmethod[(is-locked?)
@@ -2322,6 +2322,20 @@ Setting the style list is disallowed when the editor is internally
 }
 
 
+@defmethod[(size-cache-invalid)
+           void?]{
+
+This method is called when the drawing context given to the editor by
+its administrator changes in a way that makes cached size information
+(such as the width of a string) invalid.
+
+The default implementation eventually propagates the message to snips,
+and, more generally, causes @tech{location} information to be
+recalculated on demand.
+
+See also @method[editor<%> invalidate-bitmap-cache].}
+
+
 @defmethod[(style-has-changed [style (or/c (is-a?/c style<%>) false/c)])
            void?]{