diff --git a/ChangeLog b/ChangeLog
index c340e09..f7b387f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,7 @@
 2000-08-19  Bruno Haible  <bruno@linuix.math.u-bordeaux.fr>
 
+        * src/key-list.cc (Key_List::read_keys): Don't accept an empty key.
+
         * src/Makefile.in (install, installdirs, uninstall): Respect
           $(DESTDIR).
         * doc/Makefile.in (install, installdirs, uninstall): Likewise.
@@ -26,9 +28,6 @@
         * tests/Makefile.in (check-lang-syntax): Perform each test with -D
           once without and once with duplicates.
 
-        * src/key-list.cc (Key_List::output_lookup_function_body): Avoid
-          outputting a trivially satisfied test for len.
-
         * src/key-list.cc (output_keyword_entry): Avoid outputting a struct
           initializer of the form {"key",}.
 
diff --git a/src/key-list.cc b/src/key-list.cc
index 6af4231..c2b0a3e 100644
--- a/src/key-list.cc
+++ b/src/key-list.cc
@@ -320,6 +320,13 @@ Key_List::read_keys (void)
               exit (1);
             }
         }
+      /* Exit program if an empty string is used as key, since the comparison
+         expressions don't work correctly for looking up an empty string. */
+      if (min_key_len == 0)
+        {
+          fprintf (stderr, "Empty input key is not allowed.\nTo recognize an empty input key, your code should check for\nlen == 0 before calling the gperf generated lookup function.\n");
+          exit (1);
+        }
       if (option[ALLCHARS])
         option.set_keysig_size (max_key_len);
     }
@@ -1523,14 +1530,8 @@ Key_List::output_lookup_function_body (const Output_Compare& comparison)
 {
   T (Trace t ("Key_List::output_lookup_function_body");)
 
-  /* Since `len' is of type `unsigned int', we can avoid comparing it
-     against zero. */
-  if (min_key_len == 0)
-    printf ("  if (len <= MAX_WORD_LENGTH)\n");
-  else
-    printf ("  if (len <= MAX_WORD_LENGTH && len >= MIN_WORD_LENGTH)\n");
-
-  printf ("    {\n"
+  printf ("  if (len <= MAX_WORD_LENGTH && len >= MIN_WORD_LENGTH)\n"
+          "    {\n"
           "      register int key = %s (str, len);\n\n",
           option.get_hash_name ());