diff --git a/go/analysis/doc.go b/go/analysis/doc.go
index b5a301c..c5429c9 100644
--- a/go/analysis/doc.go
+++ b/go/analysis/doc.go
@@ -244,6 +244,9 @@
 Because serialized facts may appear within build outputs, the gob encoding
 of a fact must be deterministic, to avoid spurious cache misses in
 build systems that use content-addressable caches.
+The driver makes a single call to the gob encoder for all facts
+exported by a given analysis pass, so that the topology of
+shared data structures referenced by multiple facts is preserved.
 
 The Pass type has functions to import and export facts,
 associated either with an object or with a package: