diff --git a/libfwupdplugin/fu-srec-firmware.c b/libfwupdplugin/fu-srec-firmware.c
index 29210c723..55ca3bb48 100644
--- a/libfwupdplugin/fu-srec-firmware.c
+++ b/libfwupdplugin/fu-srec-firmware.c
@@ -23,12 +23,13 @@
  * See also: #FuFirmware
  */
 
-struct _FuSrecFirmware {
+typedef struct {
 	FuFirmware		 parent_instance;
 	GPtrArray		*records;
-};
+} FuSrecFirmwarePrivate;
 
-G_DEFINE_TYPE (FuSrecFirmware, fu_srec_firmware, FU_TYPE_FIRMWARE)
+G_DEFINE_TYPE_WITH_PRIVATE (FuSrecFirmware, fu_srec_firmware, FU_TYPE_FIRMWARE)
+#define GET_PRIVATE(o) (fu_srec_firmware_get_instance_private (o))
 
 /**
  * fu_srec_firmware_get_records:
@@ -46,8 +47,9 @@ G_DEFINE_TYPE (FuSrecFirmware, fu_srec_firmware, FU_TYPE_FIRMWARE)
 GPtrArray *
 fu_srec_firmware_get_records (FuSrecFirmware *self)
 {
+	FuSrecFirmwarePrivate *priv = GET_PRIVATE (self);
 	g_return_val_if_fail (FU_IS_SREC_FIRMWARE (self), NULL);
-	return self->records;
+	return priv->records;
 }
 
 static void
@@ -85,6 +87,7 @@ fu_srec_firmware_tokenize (FuFirmware *firmware, GBytes *fw,
 			   FwupdInstallFlags flags, GError **error)
 {
 	FuSrecFirmware *self = FU_SREC_FIRMWARE (firmware);
+	FuSrecFirmwarePrivate *priv = GET_PRIVATE (self);
 	const gchar *data;
 	gboolean got_eof = FALSE;
 	gsize sz = 0;
@@ -253,7 +256,7 @@ fu_srec_firmware_tokenize (FuFirmware *firmware, GBytes *fw,
 				fu_byte_array_append_uint8 (rcd->buf, tmp);
 			}
 		}
-		g_ptr_array_add (self->records, rcd);
+		g_ptr_array_add (priv->records, rcd);
 	}
 
 	/* no EOF */
@@ -276,6 +279,7 @@ fu_srec_firmware_parse (FuFirmware *firmware,
 			GError **error)
 {
 	FuSrecFirmware *self = FU_SREC_FIRMWARE (firmware);
+	FuSrecFirmwarePrivate *priv = GET_PRIVATE (self);
 	gboolean got_hdr = FALSE;
 	guint16 data_cnt = 0;
 	guint32 addr32_last = 0;
@@ -284,8 +288,8 @@ fu_srec_firmware_parse (FuFirmware *firmware,
 	g_autoptr(GByteArray) outbuf = g_byte_array_new ();
 
 	/* parse records */
-	for (guint j = 0; j < self->records->len; j++) {
-		FuSrecFirmwareRecord *rcd = g_ptr_array_index (self->records, j);
+	for (guint j = 0; j < priv->records->len; j++) {
+		FuSrecFirmwareRecord *rcd = g_ptr_array_index (priv->records, j);
 
 		/* header */
 		if (rcd->kind == FU_FIRMWARE_SREC_RECORD_KIND_S0_HEADER) {
@@ -500,14 +504,16 @@ static void
 fu_srec_firmware_finalize (GObject *object)
 {
 	FuSrecFirmware *self = FU_SREC_FIRMWARE (object);
-	g_ptr_array_unref (self->records);
+	FuSrecFirmwarePrivate *priv = GET_PRIVATE (self);
+	g_ptr_array_unref (priv->records);
 	G_OBJECT_CLASS (fu_srec_firmware_parent_class)->finalize (object);
 }
 
 static void
 fu_srec_firmware_init (FuSrecFirmware *self)
 {
-	self->records = g_ptr_array_new_with_free_func ((GFreeFunc) fu_srec_firmware_record_free);
+	FuSrecFirmwarePrivate *priv = GET_PRIVATE (self);
+	priv->records = g_ptr_array_new_with_free_func ((GFreeFunc) fu_srec_firmware_record_free);
 	fu_firmware_add_flag (FU_FIRMWARE (self), FU_FIRMWARE_FLAG_HAS_CHECKSUM);
 }
 
diff --git a/libfwupdplugin/fu-srec-firmware.h b/libfwupdplugin/fu-srec-firmware.h
index 23b115e18..cb98d74da 100644
--- a/libfwupdplugin/fu-srec-firmware.h
+++ b/libfwupdplugin/fu-srec-firmware.h
@@ -9,7 +9,12 @@
 #include "fu-firmware.h"
 
 #define FU_TYPE_SREC_FIRMWARE (fu_srec_firmware_get_type ())
-G_DECLARE_FINAL_TYPE (FuSrecFirmware, fu_srec_firmware, FU, SREC_FIRMWARE, FuFirmware)
+G_DECLARE_DERIVABLE_TYPE (FuSrecFirmware, fu_srec_firmware, FU, SREC_FIRMWARE, FuFirmware)
+
+struct _FuSrecFirmwareClass
+{
+	FuFirmwareClass		 parent_class;
+};
 
 typedef enum {
 	FU_FIRMWARE_SREC_RECORD_KIND_S0_HEADER,