diff --git a/cmd/restic/cmd_backup.go b/cmd/restic/cmd_backup.go
index 77b0925fe..f410fb1fd 100644
--- a/cmd/restic/cmd_backup.go
+++ b/cmd/restic/cmd_backup.go
@@ -98,8 +98,8 @@ type BackupOptions struct {
 
 var backupOptions BackupOptions
 
-// Error sentinel for invalid source data
-var InvalidSourceData = errors.New("Failed to read all source data during backup.")
+// ErrInvalidSourceData is used to report an incomplete backup
+var ErrInvalidSourceData = errors.New("failed to read all source data during backup")
 
 func init() {
 	cmdRoot.AddCommand(cmdBackup)
@@ -601,7 +601,7 @@ func runBackup(opts BackupOptions, gopts GlobalOptions, term *termstatus.Termina
 		p.P("snapshot %s saved\n", id.Str())
 	}
 	if !success {
-		return InvalidSourceData
+		return ErrInvalidSourceData
 	}
 
 	// Return error if any
diff --git a/cmd/restic/integration_test.go b/cmd/restic/integration_test.go
index 5ffb5ee22..5b3ca6d95 100644
--- a/cmd/restic/integration_test.go
+++ b/cmd/restic/integration_test.go
@@ -515,7 +515,7 @@ func TestBackupErrors(t *testing.T) {
 	gopts.stderr = ioutil.Discard
 	err := testRunBackupAssumeFailure(t, filepath.Dir(env.testdata), []string{"testdata"}, opts, gopts)
 	rtest.Assert(t, err != nil, "Assumed failure, but no error occured.")
-	rtest.Assert(t, err == InvalidSourceData, "Wrong error returned")
+	rtest.Assert(t, err == ErrInvalidSourceData, "Wrong error returned")
 	snapshotIDs := testRunList(t, "snapshots", env.gopts)
 	rtest.Assert(t, len(snapshotIDs) == 1,
 		"expected one snapshot, got %v", snapshotIDs)
diff --git a/cmd/restic/main.go b/cmd/restic/main.go
index 63c4dbe41..2f553c9cc 100644
--- a/cmd/restic/main.go
+++ b/cmd/restic/main.go
@@ -88,6 +88,8 @@ func main() {
 	switch {
 	case restic.IsAlreadyLocked(errors.Cause(err)):
 		fmt.Fprintf(os.Stderr, "%v\nthe `unlock` command can be used to remove stale locks\n", err)
+	case err == ErrInvalidSourceData:
+		fmt.Fprintf(os.Stderr, "Warning: %v\n", err)
 	case errors.IsFatal(errors.Cause(err)):
 		fmt.Fprintf(os.Stderr, "%v\n", err)
 	case err != nil:
@@ -106,7 +108,7 @@ func main() {
 	switch err {
 	case nil:
 		exitCode = 0
-	case InvalidSourceData:
+	case ErrInvalidSourceData:
 		exitCode = 3
 	default:
 		exitCode = 1