diff --git a/src/math/big/doc.go b/src/math/big/doc.go
index a3c23751ba4..65ed019b741 100644
--- a/src/math/big/doc.go
+++ b/src/math/big/doc.go
@@ -31,7 +31,7 @@ setters, for instance:
 
 	var z1 Int
 	z1.SetUint64(123)                 // z1 := 123
-	z2 := new(Rat).SetFloat64(1.2)    // z2 := 6/5
+	z2 := new(Rat).SetFloat64(1.25)   // z2 := 5/4
 	z3 := new(Float).SetInt(z1)       // z3 := 123.0
 
 Setters, numeric operations and predicates are represented as methods of