diff --git a/tools/java-event-log-tags.py b/tools/java-event-log-tags.py
index 552021e..c63fa20 100755
--- a/tools/java-event-log-tags.py
+++ b/tools/java-event-log-tags.py
@@ -66,7 +66,14 @@
 merged_by_name = dict([(t.tagname, t) for t in merged_tagfile.tags])
 for t in tagfile.tags:
   if t.tagnum is None:
-    t.tagnum = merged_by_name[t.tagname].tagnum
+    if t.tagname in merged_by_name:
+      t.tagnum = merged_by_name[t.tagname].tagnum
+    else:
+      # We're building something that's not being included in the
+      # product, so its tags don't appear in the merged file.  Assign
+      # them all an arbitrary number so we can emit the java and
+      # compile the (unused) package.
+      t.tagnum = 999999
 
 if "java_package" not in tagfile.options:
   tagfile.AddError("java_package option not specified", linenum=0)
diff --git a/tools/merge-event-log-tags.py b/tools/merge-event-log-tags.py
index c8f36fc..25ac697 100755
--- a/tools/merge-event-log-tags.py
+++ b/tools/merge-event-log-tags.py
@@ -137,7 +137,7 @@
 for name, t in sorted(by_tagname.iteritems()):
   if t.tagnum is None:
     while True:
-      x = (hashname(name) % (ASSIGN_LIMIT - ASSIGN_START)) + ASSIGN_START
+      x = (hashname(name) % (ASSIGN_LIMIT - ASSIGN_START - 1)) + ASSIGN_START
       if x not in by_tagnum:
         t.tagnum = x
         by_tagnum[x] = t