diff --git a/encoding/protobuf/testdata/attributes.proto.out.cue b/encoding/protobuf/testdata/attributes.proto.out.cue
index 0bdd410..9c13d65 100644
--- a/encoding/protobuf/testdata/attributes.proto.out.cue
+++ b/encoding/protobuf/testdata/attributes.proto.out.cue
@@ -14,7 +14,10 @@
 //  limitations under the License.
 package v1
 
-import "time"
+import (
+	"github.com/golang/protobuf/ptypes/duration"
+	"github.com/golang/protobuf/ptypes/timestamp"
+)
 
 //  Attributes represents a set of typed name/value pairs. Many of Mixer's
 //  API either consume and/or return attributes.
@@ -77,10 +80,10 @@
 	bytesValue?: bytes @protobuf(6,name=bytes_value)
 } | {
 	//  Used for values of type TIMESTAMP
-	timestampValue?: time.Time @protobuf(7,type=google.protobuf.Timestamp,name=timestamp_value)
+	timestampValue?: timestamp.Timestamp @protobuf(7,type=google.protobuf.Timestamp,name=timestamp_value)
 } | {
 	//  Used for values of type DURATION
-	durationValue?: time.Duration @protobuf(8,type=google.protobuf.Duration,name=duration_value)
+	durationValue?: duration.Duration @protobuf(8,type=google.protobuf.Duration,name=duration_value)
 } | {
 	//  Used for values of type STRING_MAP
 	stringMapValue?: Attributes_StringMap @protobuf(9,type=StringMap,name=string_map_value)
@@ -116,10 +119,10 @@
 	bools <_>: bool
 
 	//  Holds attributes of type TIMESTAMP
-	timestamps <_>: time.Time
+	timestamps <_>: timestamp.Timestamp
 
 	//  Holds attributes of type DURATION
-	durations <_>: time.Duration
+	durations <_>: duration.Duration
 
 	//  Holds attributes of type BYTES
 	bytes <_>: bytes
diff --git a/encoding/protobuf/testdata/client_config.proto.out.cue b/encoding/protobuf/testdata/client_config.proto.out.cue
index 66ec87a..fc7f747 100644
--- a/encoding/protobuf/testdata/client_config.proto.out.cue
+++ b/encoding/protobuf/testdata/client_config.proto.out.cue
@@ -21,8 +21,8 @@
 package client
 
 import (
+	"github.com/golang/protobuf/ptypes/duration"
 	"istio.io/api/mixer/v1"
-	"time"
 )
 
 //  Specifies the behavior when the client is unable to connect to Mixer.
@@ -36,10 +36,10 @@
 
 	//  Base time to wait between retries.  Will be adjusted by exponential
 	//  backoff and jitter.
-	baseRetryWait?: time.Duration @protobuf(3,type=google.protobuf.Duration,name=base_retry_wait)
+	baseRetryWait?: duration.Duration @protobuf(3,type=google.protobuf.Duration,name=base_retry_wait)
 
 	//  Max time to wait between retries.
-	maxRetryWait?: time.Duration @protobuf(4,type=google.protobuf.Duration,name=max_retry_wait)
+	maxRetryWait?: duration.Duration @protobuf(4,type=google.protobuf.Duration,name=max_retry_wait)
 }
 
 //  Example of single-value enum.
@@ -108,7 +108,7 @@
 
 	//  Specify refresh interval to write Mixer client statistics to Envoy share
 	//  memory. If not specified, the interval is 10 seconds.
-	statsUpdateInterval?: time.Duration @protobuf(5,type=google.protobuf.Duration,name=stats_update_interval)
+	statsUpdateInterval?: duration.Duration @protobuf(5,type=google.protobuf.Duration,name=stats_update_interval)
 
 	//  Name of the cluster that will forward check calls to a pool of mixer
 	//  servers. Defaults to "mixer_server". By using different names for
@@ -183,5 +183,5 @@
 	//  Specify report interval to send periodical reports for long TCP
 	//  connections. If not specified, the interval is 10 seconds. This interval
 	//  should not be less than 1 second, otherwise it will be reset to 1 second.
-	reportInterval?: time.Duration @protobuf(6,type=google.protobuf.Duration,name=report_interval)
+	reportInterval?: duration.Duration @protobuf(6,type=google.protobuf.Duration,name=report_interval)
 }
diff --git a/encoding/protobuf/testdata/istio.io/api/mixer/v1/attributes_proto_gen.cue b/encoding/protobuf/testdata/istio.io/api/mixer/v1/attributes_proto_gen.cue
index 0bdd410..9c13d65 100644
--- a/encoding/protobuf/testdata/istio.io/api/mixer/v1/attributes_proto_gen.cue
+++ b/encoding/protobuf/testdata/istio.io/api/mixer/v1/attributes_proto_gen.cue
@@ -14,7 +14,10 @@
 //  limitations under the License.
 package v1
 
-import "time"
+import (
+	"github.com/golang/protobuf/ptypes/duration"
+	"github.com/golang/protobuf/ptypes/timestamp"
+)
 
 //  Attributes represents a set of typed name/value pairs. Many of Mixer's
 //  API either consume and/or return attributes.
@@ -77,10 +80,10 @@
 	bytesValue?: bytes @protobuf(6,name=bytes_value)
 } | {
 	//  Used for values of type TIMESTAMP
-	timestampValue?: time.Time @protobuf(7,type=google.protobuf.Timestamp,name=timestamp_value)
+	timestampValue?: timestamp.Timestamp @protobuf(7,type=google.protobuf.Timestamp,name=timestamp_value)
 } | {
 	//  Used for values of type DURATION
-	durationValue?: time.Duration @protobuf(8,type=google.protobuf.Duration,name=duration_value)
+	durationValue?: duration.Duration @protobuf(8,type=google.protobuf.Duration,name=duration_value)
 } | {
 	//  Used for values of type STRING_MAP
 	stringMapValue?: Attributes_StringMap @protobuf(9,type=StringMap,name=string_map_value)
@@ -116,10 +119,10 @@
 	bools <_>: bool
 
 	//  Holds attributes of type TIMESTAMP
-	timestamps <_>: time.Time
+	timestamps <_>: timestamp.Timestamp
 
 	//  Holds attributes of type DURATION
-	durations <_>: time.Duration
+	durations <_>: duration.Duration
 
 	//  Holds attributes of type BYTES
 	bytes <_>: bytes
diff --git a/encoding/protobuf/testdata/istio.io/api/mixer/v1/config/client/client_config_proto_gen.cue b/encoding/protobuf/testdata/istio.io/api/mixer/v1/config/client/client_config_proto_gen.cue
index 8471bc5..07e33a3 100644
--- a/encoding/protobuf/testdata/istio.io/api/mixer/v1/config/client/client_config_proto_gen.cue
+++ b/encoding/protobuf/testdata/istio.io/api/mixer/v1/config/client/client_config_proto_gen.cue
@@ -20,8 +20,8 @@
 package client
 
 import (
+	"github.com/golang/protobuf/ptypes/duration"
 	"istio.io/api/mixer/v1"
-	"time"
 )
 
 //  Specifies the behavior when the client is unable to connect to Mixer.
@@ -35,10 +35,10 @@
 
 	//  Base time to wait between retries.  Will be adjusted by exponential
 	//  backoff and jitter.
-	baseRetryWait?: time.Duration @protobuf(3,type=google.protobuf.Duration,name=base_retry_wait)
+	baseRetryWait?: duration.Duration @protobuf(3,type=google.protobuf.Duration,name=base_retry_wait)
 
 	//  Max time to wait between retries.
-	maxRetryWait?: time.Duration @protobuf(4,type=google.protobuf.Duration,name=max_retry_wait)
+	maxRetryWait?: duration.Duration @protobuf(4,type=google.protobuf.Duration,name=max_retry_wait)
 }
 
 //  Example of single-value enum.
@@ -107,7 +107,7 @@
 
 	//  Specify refresh interval to write Mixer client statistics to Envoy share
 	//  memory. If not specified, the interval is 10 seconds.
-	statsUpdateInterval?: time.Duration @protobuf(5,type=google.protobuf.Duration,name=stats_update_interval)
+	statsUpdateInterval?: duration.Duration @protobuf(5,type=google.protobuf.Duration,name=stats_update_interval)
 
 	//  Name of the cluster that will forward check calls to a pool of mixer
 	//  servers. Defaults to "mixer_server". By using different names for
@@ -182,5 +182,5 @@
 	//  Specify report interval to send periodical reports for long TCP
 	//  connections. If not specified, the interval is 10 seconds. This interval
 	//  should not be less than 1 second, otherwise it will be reset to 1 second.
-	reportInterval?: time.Duration @protobuf(6,type=google.protobuf.Duration,name=report_interval)
+	reportInterval?: duration.Duration @protobuf(6,type=google.protobuf.Duration,name=report_interval)
 }
diff --git a/encoding/protobuf/testdata/istio.io/api/mixer/v1/mixer_proto_gen.cue b/encoding/protobuf/testdata/istio.io/api/mixer/v1/mixer_proto_gen.cue
index 9c4bf1c..335b311 100644
--- a/encoding/protobuf/testdata/istio.io/api/mixer/v1/mixer_proto_gen.cue
+++ b/encoding/protobuf/testdata/istio.io/api/mixer/v1/mixer_proto_gen.cue
@@ -17,8 +17,8 @@
 package v1
 
 import (
+	"github.com/golang/protobuf/ptypes/duration"
 	"google.golang.org/genproto/googleapis/rpc/status"
-	"time"
 )
 
 //  Used to get a thumbs-up/thumbs-down before performing an action.
@@ -70,7 +70,7 @@
 	status?: __status.Status @protobuf(1,type=google.rpc.Status,"(gogoproto.nullable)=false")
 
 	//  The amount of time for which this result can be considered valid.
-	validDuration?: time.Duration @protobuf(2,type=google.protobuf.Duration,name=valid_duration,"(gogoproto.nullable)=false","(gogoproto.stdduration)")
+	validDuration?: duration.Duration @protobuf(2,type=google.protobuf.Duration,name=valid_duration,"(gogoproto.nullable)=false","(gogoproto.stdduration)")
 
 	//  The number of uses for which this result can be considered valid.
 	validUseCount?: int32 @protobuf(3,name=valid_use_count)
@@ -88,7 +88,7 @@
 //  Expresses the result of a quota allocation.
 CheckResponse_QuotaResult: {
 	//  The amount of time for which this result can be considered valid.
-	validDuration?: time.Duration @protobuf(1,type=google.protobuf.Duration,name=valid_duration,"(gogoproto.nullable)=false","(gogoproto.stdduration)")
+	validDuration?: duration.Duration @protobuf(1,type=google.protobuf.Duration,name=valid_duration,"(gogoproto.nullable)=false","(gogoproto.stdduration)")
 
 	//  The amount of granted quota. When `QuotaParams.best_effort` is true, this will be >= 0.
 	//  If `QuotaParams.best_effort` is false, this will be either 0 or >= `QuotaParams.amount`.
diff --git a/encoding/protobuf/testdata/istio.io/api/pkg/google.golang.org/genproto/googleapis/rpc/status/status_proto_gen.cue b/encoding/protobuf/testdata/istio.io/api/pkg/google.golang.org/genproto/googleapis/rpc/status/status_proto_gen.cue
index e1348a8..f8e8246 100644
--- a/encoding/protobuf/testdata/istio.io/api/pkg/google.golang.org/genproto/googleapis/rpc/status/status_proto_gen.cue
+++ b/encoding/protobuf/testdata/istio.io/api/pkg/google.golang.org/genproto/googleapis/rpc/status/status_proto_gen.cue
@@ -14,6 +14,8 @@
 //  limitations under the License.
 package status
 
+import "github.com/golang/protobuf/ptypes/any"
+
 //  The `Status` type defines a logical error model that is suitable for
 //  different programming environments, including REST APIs and RPC APIs. It is
 //  used by [gRPC](https://github.com/grpc). The error model is designed to be:
@@ -80,5 +82,5 @@
 
 	//  A list of messages that carry the error details.  There is a common set of
 	//  message types for APIs to use.
-	details?: [...] @protobuf(3,type=google.protobuf.Any)
+	details?: [...any.Any] @protobuf(3,type=google.protobuf.Any)
 }
diff --git a/encoding/protobuf/types.go b/encoding/protobuf/types.go
index 4538a01..c6c8548 100644
--- a/encoding/protobuf/types.go
+++ b/encoding/protobuf/types.go
@@ -63,18 +63,6 @@
 	switch file {
 	case "gogoproto/gogo.proto":
 
-	case "google/protobuf/duration.proto":
-		p.setBuiltin("google.protobuf.Duration", "time.Duration", timePkg)
-
-	case "google/protobuf/timestamp.proto":
-		p.setBuiltin("google.protobuf.Timestamp", "time.Time", timePkg)
-
-	case "google/protobuf/any.proto":
-		p.setBuiltin("google.protobuf.Any", "_", nil)
-
-	case "google/protobuf/empty.proto":
-		p.setBuiltin("google.protobuf.Empty", "{}", nil)
-
 	default:
 		if required {
 			failf(pos, "import %q not found", file)