--- a/memory/replace/dmd/DMD.h
+++ b/memory/replace/dmd/DMD.h
@@ -50,17 +50,20 @@ ClearReports();
 
 // Checks which heap blocks have been reported, and dumps a human-readable
 // summary (via |aWrite|).  If |aWrite| is nullptr it will dump to stderr.
 // Beware:  this output may have very long lines.
 MOZ_EXPORT void
 Dump(Writer aWriter);
 
 // A useful |WriterFun|.  If |fp| is a FILE* you want |Dump|'s output to be
-// written to, call |Dump(FpWrite, fp)|.
+// written to, call:
+//
+//   dmd::Writer writer(FpWrite, fp);
+//   dmd::Dump(writer);
 MOZ_EXPORT void
 FpWrite(void* aFp, const char* aFmt, va_list aAp);
 
 struct Sizes
 {
   size_t mStackTracesUsed;
   size_t mStackTracesUnused;
   size_t mStackTraceTable;