diff --git a/descriptor/descriptor.go b/descriptor/descriptor.go
index c3c4a2b87e..ffde8a6508 100644
--- a/descriptor/descriptor.go
+++ b/descriptor/descriptor.go
@@ -79,14 +79,9 @@ func deriveRawDescriptor(d protoreflect.Descriptor) ([]byte, []int) {
 	}
 
 	// Obtain the raw file descriptor.
-	var raw []byte
-	switch fd := d.(type) {
-	case interface{ ProtoLegacyRawDesc() []byte }:
-		raw = fd.ProtoLegacyRawDesc()
-	case protoreflect.FileDescriptor:
-		raw, _ = proto.Marshal(protodesc.ToFileDescriptorProto(fd))
-	}
-	file := protoimpl.X.CompressGZIP(raw)
+	fd := d.(protoreflect.FileDescriptor)
+	b, _ := proto.Marshal(protodesc.ToFileDescriptorProto(fd))
+	file := protoimpl.X.CompressGZIP(b)
 
 	// Reverse the indexes, since we populated it in reverse.
 	for i, j := 0, len(idxs)-1; i < j; i, j = i+1, j-1 {
diff --git a/proto/registry.go b/proto/registry.go
index 1e7ff64205..066b4323b4 100644
--- a/proto/registry.go
+++ b/proto/registry.go
@@ -13,6 +13,7 @@ import (
 	"strings"
 	"sync"
 
+	"google.golang.org/protobuf/reflect/protodesc"
 	"google.golang.org/protobuf/reflect/protoreflect"
 	"google.golang.org/protobuf/reflect/protoregistry"
 	"google.golang.org/protobuf/runtime/protoimpl"
@@ -62,14 +63,7 @@ func FileDescriptor(s filePath) fileDescGZIP {
 	// Find the descriptor in the v2 registry.
 	var b []byte
 	if fd, _ := protoregistry.GlobalFiles.FindFileByPath(s); fd != nil {
-		if fd, ok := fd.(interface{ ProtoLegacyRawDesc() []byte }); ok {
-			b = fd.ProtoLegacyRawDesc()
-		} else {
-			// TODO: Use protodesc.ToFileDescriptorProto to construct
-			// a descriptorpb.FileDescriptorProto and marshal it.
-			// However, doing so causes the proto package to have a dependency
-			// on descriptorpb, leading to cyclic dependency issues.
-		}
+		b, _ = Marshal(protodesc.ToFileDescriptorProto(fd))
 	}
 
 	// Locally cache the raw descriptor form for the file.