diff --git a/include/patchlevel.h b/include/patchlevel.h
index 74f586c56..130ae8beb 100644
--- a/include/patchlevel.h
+++ b/include/patchlevel.h
@@ -17,7 +17,7 @@
  * Incrementing EDITLEVEL can be used to force invalidation of old bones
  * and save files.
  */
-#define EDITLEVEL 99
+#define EDITLEVEL 100
 
 /*
  * Development status possibilities.
diff --git a/src/light.c b/src/light.c
index 85c2beb2c..13708f8c7 100644
--- a/src/light.c
+++ b/src/light.c
@@ -473,6 +473,14 @@ relink_light_sources(boolean ghostly)
     for (ls = gl.light_base; ls; ls = ls->next) {
         if (ls->flags & LSF_NEEDS_FIXUP) {
             if (ls->type == LS_OBJECT || ls->type == LS_MONSTER) {
+                if (!ls->id.a_uint) {
+                    /* it was possible to get stuck in this loop on bad
+                     * savefile data load and repeatedly prompt the player
+                     * for a key press after displaying an impossible message.
+                     * Consider this bad data from a savefile and panic() */
+                     panic("relink_light_sources: id = 0, type = %d",
+                           (int) ls->type);
+                }
                 if (ghostly) {
                     if (!lookup_id_mapping(ls->id.a_uint, &nid))
                         impossible("relink_light_sources: no id mapping");