--- compat.gperf
+++ compat.gperf
@@ -46,7 +46,11 @@
 
 static id3_compat_func_t translate_TCON;
 %}
-struct id3_compat;
+struct id3_compat {
+  char const *id;
+  char const *equiv;
+  id3_compat_func_t *translate;
+};
 %%
 #
 # ID3v2.2 and ID3v2.3 frames
--- frametype.gperf
+++ frametype.gperf
@@ -269,7 +269,13 @@
 FRAMETYPE(unknown,      unknown, PRESERVE, "Unknown frame");
 FRAMETYPE(obsolete,     unknown, OBSOLETE, "Obsolete frame");
 %}
-struct id3_frametype;
+struct id3_frametype {
+  char const *id;
+  unsigned int nfields;
+  enum id3_field_type const *fields;
+  int defaultflags;
+  char const *description;
+};
 %%
 #
 # ID3v2.4 frames