diff --git a/encoding/protojson/encode_test.go b/encoding/protojson/encode_test.go
index 5e1570a4..f1a05fe1 100644
--- a/encoding/protojson/encode_test.go
+++ b/encoding/protojson/encode_test.go
@@ -1255,6 +1255,18 @@ func TestMarshal(t *testing.T) {
   {},
   []
 ]`,
+	}, {
+		desc:    "Value with NaN",
+		input:   structpb.NewNumberValue(math.NaN()),
+		wantErr: true,
+	}, {
+		desc:    "Value with -Inf",
+		input:   structpb.NewNumberValue(math.Inf(-1)),
+		wantErr: true,
+	}, {
+		desc:    "Value with +Inf",
+		input:   structpb.NewNumberValue(math.Inf(+1)),
+		wantErr: true,
 	}, {
 		desc:  "Struct with nil map",
 		input: &structpb.Struct{},
diff --git a/encoding/protojson/well_known_types.go b/encoding/protojson/well_known_types.go
index 7a2fde33..72924a90 100644
--- a/encoding/protojson/well_known_types.go
+++ b/encoding/protojson/well_known_types.go
@@ -7,6 +7,7 @@ package protojson
 import (
 	"bytes"
 	"fmt"
+	"math"
 	"strconv"
 	"strings"
 	"time"
@@ -495,6 +496,11 @@ func (e encoder) marshalKnownValue(m pref.Message) error {
 	if fd == nil {
 		return errors.New("%s: none of the oneof fields is set", genid.Value_message_fullname)
 	}
+	if fd.Number() == genid.Value_NumberValue_field_number {
+		if v := m.Get(fd).Float(); math.IsNaN(v) || math.IsInf(v, 0) {
+			return errors.New("%s: invalid %v value", genid.Value_NumberValue_field_fullname, v)
+		}
+	}
 	return e.marshalSingular(m.Get(fd), fd)
 }