diff --git a/include/sym.h b/include/sym.h
index 4292236eb..15884d404 100644
--- a/include/sym.h
+++ b/include/sym.h
@@ -56,6 +56,7 @@ struct symdef {
 };
 
 enum symparse_range {
+    SYM_INVALID = 0,
     SYM_CONTROL = 1, /* start/finish markers */
     SYM_PCHAR = 2,   /* index into showsyms  */
     SYM_OC = 3,      /* index into oc_syms   */
diff --git a/include/wintype.h b/include/wintype.h
index 794be9ad3..f00fb08ce 100644
--- a/include/wintype.h
+++ b/include/wintype.h
@@ -208,6 +208,7 @@ enum to_core_flags {
 };
 
 enum from_core_requests {
+    invalid_core_request = 0,
     set_mode             = 1,
     request_settings     = 2,
     set_menu_promptstyle = 3,
diff --git a/src/symbols.c b/src/symbols.c
index 8172f73e2..397180e54 100644
--- a/src/symbols.c
+++ b/src/symbols.c
@@ -426,7 +426,7 @@ const struct symparse loadsyms[] = {
     { SYM_OTH, SYM_INVISIBLE + SYM_OFF_X, "S_invisible" },
     { SYM_OTH, SYM_PET_OVERRIDE + SYM_OFF_X, "S_pet_override" },
     { SYM_OTH, SYM_HERO_OVERRIDE + SYM_OFF_X, "S_hero_override" },
-    { 0, 0, (const char *) 0 } /* fence post */
+    { SYM_INVALID, 0, (const char *) 0 } /* fence post */
 };
 
 boolean