diff --git a/proto/all_test.go b/proto/all_test.go
index eec5841..9ae811e 100644
--- a/proto/all_test.go
+++ b/proto/all_test.go
@@ -1670,7 +1670,7 @@
 	}
 }
 
-func TestErrRequiredNotSet(t *testing.T) {
+func TestRequiredNotSetError(t *testing.T) {
 	pb := initGoTest(false)
 	pb.RequiredField.Label = nil
 	pb.F_Int32Required = nil
@@ -1695,8 +1695,8 @@
 
 	o := old()
 	bytes, err := Marshal(pb)
-	if _, ok := err.(*ErrRequiredNotSet); !ok {
-		fmt.Printf("marshal-1 err = %v, want *ErrRequiredNotSet", err)
+	if _, ok := err.(*RequiredNotSetError); !ok {
+		fmt.Printf("marshal-1 err = %v, want *RequiredNotSetError", err)
 		o.DebugPrint("", bytes)
 		t.Fatalf("expected = %s", expected)
 	}
@@ -1711,8 +1711,8 @@
 	// Now test Unmarshal by recreating the original buffer.
 	pbd := new(GoTest)
 	err = Unmarshal(bytes, pbd)
-	if _, ok := err.(*ErrRequiredNotSet); !ok {
-		t.Fatalf("unmarshal err = %v, want *ErrRequiredNotSet", err)
+	if _, ok := err.(*RequiredNotSetError); !ok {
+		t.Fatalf("unmarshal err = %v, want *RequiredNotSetError", err)
 		o.DebugPrint("", bytes)
 		t.Fatalf("string = %s", expected)
 	}
@@ -1720,8 +1720,8 @@
 		t.Errorf("unmarshal wrong err msg: %v", err)
 	}
 	bytes, err = Marshal(pbd)
-	if _, ok := err.(*ErrRequiredNotSet); !ok {
-		t.Errorf("marshal-2 err = %v, want *ErrRequiredNotSet", err)
+	if _, ok := err.(*RequiredNotSetError); !ok {
+		t.Errorf("marshal-2 err = %v, want *RequiredNotSetError", err)
 		o.DebugPrint("", bytes)
 		t.Fatalf("string = %s", expected)
 	}
diff --git a/proto/decode.go b/proto/decode.go
index 3c58cfb..59189d7 100644
--- a/proto/decode.go
+++ b/proto/decode.go
@@ -441,7 +441,7 @@
 			// Not enough information to determine the exact field. If we use extra
 			// CPU, we could determine the field only if the missing required field
 			// has a tag <= 64 and we check reqFields.
-			return &ErrRequiredNotSet{"{Unknown}"}
+			return &RequiredNotSetError{"{Unknown}"}
 		}
 	}
 	return err
diff --git a/proto/encode.go b/proto/encode.go
index 1cc62e9..2a249c8 100644
--- a/proto/encode.go
+++ b/proto/encode.go
@@ -42,20 +42,20 @@
 	"sort"
 )
 
-// ErrRequiredNotSet is the error returned if Marshal is called with
+// RequiredNotSetError is the error returned if Marshal is called with
 // a protocol buffer struct whose required fields have not
 // all been initialized. It is also the error returned if Unmarshal is
 // called with an encoded protocol buffer that does not include all the
 // required fields.
 //
-// When printed, ErrRequiredNotSet reports the first unset required field in a
+// When printed, RequiredNotSetError reports the first unset required field in a
 // message. If the field cannot be precisely determined, it is reported as
 // "{Unknown}".
-type ErrRequiredNotSet struct {
+type RequiredNotSetError struct {
 	field string
 }
 
-func (e *ErrRequiredNotSet) Error() string {
+func (e *RequiredNotSetError) Error() string {
 	return fmt.Sprintf("proto: required field %q not set", e.field)
 }
 
@@ -590,7 +590,7 @@
 			if err != nil {
 				if err == ErrNil {
 					if p.Required && state.err == nil {
-						state.err = &ErrRequiredNotSet{p.Name}
+						state.err = &RequiredNotSetError{p.Name}
 					}
 				} else if !state.shouldContinue(err, p) {
 					return err
@@ -617,7 +617,7 @@
 }
 
 // shouldContinue reports whether encoding should continue upon encountering the
-// given error. If the error is ErrRequiredNotSet, shouldContinue returns true
+// given error. If the error is RequiredNotSetError, shouldContinue returns true
 // and, if this is the first appearance of that error, remembers it for future
 // reporting.
 //
@@ -625,13 +625,13 @@
 // field with the error.
 func (s *errorState) shouldContinue(err error, prop *Properties) bool {
 	// Ignore unset required fields.
-	reqNotSet, ok := err.(*ErrRequiredNotSet)
+	reqNotSet, ok := err.(*RequiredNotSetError)
 	if !ok {
 		return false
 	}
 	if s.err == nil {
 		if prop != nil {
-			err = &ErrRequiredNotSet{prop.Name + "." + reqNotSet.field}
+			err = &RequiredNotSetError{prop.Name + "." + reqNotSet.field}
 		}
 		s.err = err
 	}