diff --git a/proto/equal.go b/proto/equal.go
index 1aca6703..44f840a8 100644
--- a/proto/equal.go
+++ b/proto/equal.go
@@ -6,6 +6,7 @@ package proto
 
 import (
 	"bytes"
+	"math"
 	"reflect"
 
 	"google.golang.org/protobuf/internal/encoding/wire"
@@ -13,14 +14,16 @@ import (
 )
 
 // Equal reports whether two messages are equal.
+// If two messages marshal to the same bytes under deterministic serialization,
+// then Equal is guaranteed to report true.
 //
 // Two messages are equal if they belong to the same message descriptor,
 // have the same set of populated known and extension field values,
 // and the same set of unknown fields values.
 //
 // Scalar values are compared with the equivalent of the == operator in Go,
-// except bytes values which are compared using bytes.Equal.
-// Note that this means that floating point NaNs are considered inequal.
+// except bytes values which are compared using bytes.Equal and
+// floating point values which specially treat NaNs as equal.
 // Message values are compared by recursively calling Equal.
 // Lists are equal if each element value is also equal.
 // Maps are equal if they have the same set of keys, where the pair of values
@@ -104,6 +107,13 @@ func equalValue(fd pref.FieldDescriptor, x, y pref.Value) bool {
 		return equalMessage(x.Message(), y.Message())
 	case fd.Kind() == pref.BytesKind:
 		return bytes.Equal(x.Bytes(), y.Bytes())
+	case fd.Kind() == pref.FloatKind, fd.Kind() == pref.DoubleKind:
+		fx := x.Float()
+		fy := y.Float()
+		if math.IsNaN(fx) || math.IsNaN(fy) {
+			return math.IsNaN(fx) && math.IsNaN(fy)
+		}
+		return fx == fy
 	default:
 		return x.Interface() == y.Interface()
 	}
diff --git a/proto/equal_test.go b/proto/equal_test.go
index 40507a9f..3afca838 100644
--- a/proto/equal_test.go
+++ b/proto/equal_test.go
@@ -5,6 +5,7 @@
 package proto_test
 
 import (
+	"math"
 	"testing"
 
 	"google.golang.org/protobuf/internal/encoding/pack"
@@ -74,6 +75,14 @@ var inequalities = []struct{ a, b proto.Message }{
 		&testpb.TestAllTypes{OptionalDouble: proto.Float64(1)},
 		&testpb.TestAllTypes{OptionalDouble: proto.Float64(2)},
 	},
+	{
+		&testpb.TestAllTypes{OptionalFloat: proto.Float32(float32(math.NaN()))},
+		&testpb.TestAllTypes{OptionalFloat: proto.Float32(0)},
+	},
+	{
+		&testpb.TestAllTypes{OptionalDouble: proto.Float64(float64(math.NaN()))},
+		&testpb.TestAllTypes{OptionalDouble: proto.Float64(0)},
+	},
 	{
 		&testpb.TestAllTypes{OptionalBool: proto.Bool(true)},
 		&testpb.TestAllTypes{OptionalBool: proto.Bool(false)},