diff --git a/em-format/e-mail-formatter-print-headers.c b/em-format/e-mail-formatter-print-headers.c
index 8f1745b05e..17e1f78291 100644
--- a/em-format/e-mail-formatter-print-headers.c
+++ b/em-format/e-mail-formatter-print-headers.c
@@ -24,8 +24,7 @@
 
 #include <glib/gi18n-lib.h>
 
-#include <em-format/e-mail-formatter-extension.h>
-#include <em-format/e-mail-formatter.h>
+#include <em-format/e-mail-formatter-print.h>
 #include <em-format/e-mail-formatter-utils.h>
 #include <em-format/e-mail-inline-filter.h>
 #include <libemail-engine/e-mail-utils.h>
@@ -41,7 +40,7 @@ typedef EMailFormatterExtensionClass EMailFormatterPrintHeadersClass;
 G_DEFINE_TYPE (
 	EMailFormatterPrintHeaders,
 	e_mail_formatter_print_headers,
-	E_TYPE_MAIL_FORMATTER_EXTENSION)
+	E_TYPE_MAIL_FORMATTER_PRINT_EXTENSION)
 
 static const gchar *formatter_mime_types[] = {
 	"application/vnd.evolution.headers",
diff --git a/em-format/e-mail-formatter-print.c b/em-format/e-mail-formatter-print.c
index 8e56445ccd..7016b2fb78 100644
--- a/em-format/e-mail-formatter-print.c
+++ b/em-format/e-mail-formatter-print.c
@@ -282,3 +282,20 @@ e_mail_formatter_print_get_type (void)
 	return type;
 }
 
+/* ------------------------------------------------------------------------- */
+
+G_DEFINE_ABSTRACT_TYPE (
+	EMailFormatterPrintExtension,
+	e_mail_formatter_print_extension,
+	E_TYPE_MAIL_FORMATTER_EXTENSION)
+
+static void
+e_mail_formatter_print_extension_class_init (EMailFormatterPrintExtensionClass *class)
+{
+}
+
+static void
+e_mail_formatter_print_extension_init (EMailFormatterPrintExtension *extension)
+{
+}
+
diff --git a/em-format/e-mail-formatter-print.h b/em-format/e-mail-formatter-print.h
index 1783cc068a..ca67a13137 100644
--- a/em-format/e-mail-formatter-print.h
+++ b/em-format/e-mail-formatter-print.h
@@ -16,10 +16,11 @@
  *
  */
 
-#ifndef E_MAIL_FORMATTER_PRINT_H_
-#define E_MAIL_FORMATTER_PRINT_H_
+#ifndef E_MAIL_FORMATTER_PRINT_H
+#define E_MAIL_FORMATTER_PRINT_H
 
 #include <em-format/e-mail-formatter.h>
+#include <em-format/e-mail-formatter-extension.h>
 
 /* Standard GObject macros */
 #define E_TYPE_MAIL_FORMATTER_PRINT \
@@ -54,10 +55,32 @@ struct _EMailFormatterPrintClass {
 	EMailFormatterClass parent_class;
 };
 
-GType		e_mail_formatter_print_get_type	(void);
-
-EMailFormatter *	e_mail_formatter_print_new	(void);
+GType		e_mail_formatter_print_get_type	(void) G_GNUC_CONST;
+EMailFormatter *
+		e_mail_formatter_print_new	(void);
 
 G_END_DECLS
 
-#endif /* E_MAIL_FORMATTER_PRINT_H_ */
+/* ------------------------------------------------------------------------- */
+
+/* Standard GObject macros */
+#define E_TYPE_MAIL_FORMATTER_PRINT_EXTENSION \
+	(e_mail_formatter_print_extension_get_type ())
+
+G_BEGIN_DECLS
+
+/**
+ * EMailFormatterPrintExtension:
+ *
+ * This is an abstract base type for formatter extensions which are
+ * intended only for use by #EMailFormatterPrint.
+ **/
+typedef EMailFormatterExtension EMailFormatterPrintExtension;
+typedef EMailFormatterExtensionClass EMailFormatterPrintExtensionClass;
+
+GType		e_mail_formatter_print_extension_get_type
+						(void) G_GNUC_CONST;
+
+G_END_DECLS
+
+#endif /* E_MAIL_FORMATTER_PRINT_H */