diff --git a/src/fmt/doc.go b/src/fmt/doc.go
index ea2da97da6..c47bee1080 100644
--- a/src/fmt/doc.go
+++ b/src/fmt/doc.go
@@ -16,6 +16,7 @@ General:
 	%v	the value in a default format
 		when printing structs, the plus flag (%+v) adds field names
 	%#v	a Go-syntax representation of the value
+		(floating-point infinities and NaNs print as ±Inf and NaN)
 	%T	a Go-syntax representation of the type of the value
 	%%	a literal percent sign; consumes no value