diff --git a/decoder.go b/decoder.go
index 8c96f53..31ee0d6 100644
--- a/decoder.go
+++ b/decoder.go
@@ -22,5 +22,9 @@ func (d *Decoder) Decode(in []byte) (bandwidth Bandwidth, isStereo bool, frames
 		return 0, false, nil, fmt.Errorf("%w: %d", errUnsupportedFrameCode, tocHeader.frameCode())
 	}
 
+	if cfg.mode() != configurationModeCELTOnly {
+		return 0, false, nil, fmt.Errorf("%w: %d", errUnsupportedConfigurationMode, cfg.mode())
+	}
+
 	return cfg.bandwidth(), tocHeader.isStereo(), nil, nil
 }
diff --git a/errors.go b/errors.go
index ff17761..6f15636 100644
--- a/errors.go
+++ b/errors.go
@@ -9,4 +9,6 @@ var (
 	errTooShortForArbitraryLengthFrames       = errors.New("packet is too short to contain arbitrary length frames")
 	errArbitraryLengthFrameVBRUnsupported     = errors.New("arbitrary length frames with VBR is unsupported")
 	errArbitraryLengthFramePaddingUnsupported = errors.New("arbitrary length frames with padding is unsupported")
+
+	errUnsupportedConfigurationMode = errors.New("unsupported configuration mode")
 )