diff --git a/libgimpthumb/gimpthumb-enums.h b/libgimpthumb/gimpthumb-enums.h
index b86b8a63e8..3d72a8d035 100644
--- a/libgimpthumb/gimpthumb-enums.h
+++ b/libgimpthumb/gimpthumb-enums.h
@@ -85,8 +85,8 @@ typedef enum
  * GimpThumbState:
  * @GIMP_THUMB_STATE_UNKNOWN:   nothing is known about the file/thumbnail
  * @GIMP_THUMB_STATE_REMOTE:    the file is on a remote file system
- * @GIMP_THUMB_STATE_FOLDER:
- * @GIMP_THUMB_STATE_SPECIAL:
+ * @GIMP_THUMB_STATE_FOLDER:    the file is a directory
+ * @GIMP_THUMB_STATE_SPECIAL:   the file is a special file
  * @GIMP_THUMB_STATE_NOT_FOUND: the file/thumbnail doesn't exist
  * @GIMP_THUMB_STATE_EXISTS:    the file/thumbnail exists
  * @GIMP_THUMB_STATE_OLD:       the thumbnail may be outdated
diff --git a/libgimpthumb/gimpthumb-utils.c b/libgimpthumb/gimpthumb-utils.c
index 15b946c234..07252ab6aa 100644
--- a/libgimpthumb/gimpthumb-utils.c
+++ b/libgimpthumb/gimpthumb-utils.c
@@ -186,8 +186,8 @@ gimp_thumb_get_thumb_dir (GimpThumbSize  size)
 
 /**
  * gimp_thumb_get_thumb_dir_local:
- * @dirname:
- * @size: a GimpThumbSize
+ * @dirname: the basename of the dir, without the actual dirname itself
+ * @size:    a GimpThumbSize
  *
  * Retrieve the name of the local thumbnail folder for a specific
  * size.  Unlike gimp_thumb_get_thumb_dir() the returned string is not
@@ -260,9 +260,9 @@ gimp_thumb_ensure_thumb_dir (GimpThumbSize   size,
 
 /**
  * gimp_thumb_ensure_thumb_dir_local:
- * @dirname:
- * @size: a GimpThumbSize
- * @error: return location for possible errors
+ * @dirname: the basename of the dir, without the actual dirname itself
+ * @size:    a GimpThumbSize
+ * @error:   return location for possible errors
  *
  * This function checks if the directory that is required to store
  * local thumbnails for a particular @size exist and attempts to
diff --git a/libgimpthumb/gimpthumbnail.c b/libgimpthumb/gimpthumbnail.c
index c64b3a0644..ce67268855 100644
--- a/libgimpthumb/gimpthumbnail.c
+++ b/libgimpthumb/gimpthumbnail.c
@@ -169,6 +169,8 @@ gimp_thumbnail_class_init (GimpThumbnailClass *klass)
   /**
    * GimpThumbnail::image-mimetype:
    *
+   * Image mimetype
+   *
    * Since: GIMP 2.2
    **/
   g_object_class_install_property (object_class,
diff --git a/libgimpthumb/gimpthumbnail.h b/libgimpthumb/gimpthumbnail.h
index e8eeb7db16..cc957a18f7 100644
--- a/libgimpthumb/gimpthumbnail.h
+++ b/libgimpthumb/gimpthumbnail.h
@@ -38,6 +38,12 @@ G_BEGIN_DECLS
 
 typedef struct _GimpThumbnailClass GimpThumbnailClass;
 
+/**
+ * GimpThumbnail:
+ *
+ * All members of #GimpThumbnail are private and should only be accessed
+ * using object properties.
+ **/
 struct _GimpThumbnail
 {
   GObject         parent_instance;