--- a/.lldbinit
+++ b/.lldbinit
@@ -1,9 +1,11 @@
 # .lldbinit file for debugging Mozilla
 
 # Mozilla's use of UNIFIED_SOURCES to include multiple source files into a
 # single compiled file breaks lldb breakpoint setting. This works around that.
 # See http://lldb.llvm.org/troubleshooting.html for more info.
 settings set target.inline-breakpoint-strategy always
 
-# Deduce the concrete types of objects and pointers when printing them.
+# Show the dynamic type of an object when using "expr".  This, for example,
+# will show a variable declared as "nsIFrame *" that points to an nsBlockFrame
+# object as being of type "nsBlockFrame *" rather than "nsIFrame *".
 settings set target.prefer-dynamic-value run-target