diff --git a/field.go b/field.go
index 2ca08b752..f24f8d854 100644
--- a/field.go
+++ b/field.go
@@ -75,9 +75,8 @@ func Bool(key string, val bool) Field {
 	return Field{key: key, fieldType: boolType, ival: ival}
 }
 
-// Float64 constructs a Field with the given key and value. The floating-point
-// value is encoded using strconv.FormatFloat's 'g' option (exponential notation
-// for large exponents, grade-school notation otherwise).
+// Float64 constructs a Field with the given key and value. The way the
+// floating-point value is represented is encoder-dependent.
 func Float64(key string, val float64) Field {
 	return Field{key: key, fieldType: floatType, ival: int64(math.Float64bits(val))}
 }
diff --git a/json_encoder.go b/json_encoder.go
index c3183a2e9..94a83ea28 100644
--- a/json_encoder.go
+++ b/json_encoder.go
@@ -106,8 +106,8 @@ func (enc *jsonEncoder) AddInt64(key string, val int64) {
 
 // AddFloat64 adds a string key and float64 value to the encoder's fields. The
 // key is JSON-escaped, and the floating-point value is encoded using
-// strconv.FormatFloat's 'g' option (exponential notation for large exponents,
-// grade-school notation otherwise).
+// strconv.FormatFloat's 'f' option (always use grade-school notation, even for
+// large exponents).
 func (enc *jsonEncoder) AddFloat64(key string, val float64) {
 	enc.addKey(key)
 	switch {
@@ -118,13 +118,11 @@ func (enc *jsonEncoder) AddFloat64(key string, val float64) {
 	case math.IsInf(val, -1):
 		enc.bytes = append(enc.bytes, `"-Inf"`...)
 	default:
-		enc.bytes = strconv.AppendFloat(enc.bytes, val, 'g', -1, 64)
+		enc.bytes = strconv.AppendFloat(enc.bytes, val, 'f', -1, 64)
 	}
 }
 
 // AddMarshaler adds a LogMarshaler to the encoder's fields.
-//
-// TODO: Encode the error into the message instead of returning.
 func (enc *jsonEncoder) AddMarshaler(key string, obj LogMarshaler) error {
 	enc.addKey(key)
 	enc.bytes = append(enc.bytes, '{')
diff --git a/json_encoder_test.go b/json_encoder_test.go
index 6de153c7d..76c743bce 100644
--- a/json_encoder_test.go
+++ b/json_encoder_test.go
@@ -103,7 +103,7 @@ func TestJSONAddInt64(t *testing.T) {
 func TestJSONAddFloat64(t *testing.T) {
 	withJSONEncoder(func(enc *jsonEncoder) {
 		enc.AddFloat64("baz", 1e10)
-		assertJSON(t, `"foo":"bar","baz":1e+10`, enc)
+		assertJSON(t, `"foo":"bar","baz":10000000000`, enc)
 
 		// Keys should be escaped.
 		enc.truncate()