Index: ext/rtree/rtree.c
==================================================================
--- ext/rtree/rtree.c
+++ ext/rtree/rtree.c
@@ -92,10 +92,13 @@
 typedef union RtreeCoord RtreeCoord;
 typedef struct RtreeSearchPoint RtreeSearchPoint;
 
 /* The rtree may have between 1 and RTREE_MAX_DIMENSIONS dimensions. */
 #define RTREE_MAX_DIMENSIONS 5
+
+/* Maximum number of auxiliary columns */
+#define RTREE_MAX_AUX_COLUMN 100
 
 /* Size of hash table Rtree.aHash. This hash table is not expected to
 ** ever contain very many entries, so a fixed number of buckets is 
 ** used.
 */
@@ -3552,14 +3555,15 @@
   const char *aErrMsg[] = {
     0,                                                    /* 0 */
     "Wrong number of columns for an rtree table",         /* 1 */
     "Too few columns for an rtree table",                 /* 2 */
     "Too many columns for an rtree table",                /* 3 */
-    "AUX: columns must be last"                           /* 4 */
+    "Auxiliary rtree columns must be last"                /* 4 */
   };
 
-  if( argc>=256 ){
+  assert( RTREE_MAX_AUX_COLUMN<256 ); /* Aux columns counted by a u8 */
+  if( argc>RTREE_MAX_AUX_COLUMN+3 ){
     *pzErr = sqlite3_mprintf("%s", aErrMsg[3]);
     return SQLITE_ERROR;
   }
 
   sqlite3_vtab_config(db, SQLITE_VTAB_CONSTRAINT_SUPPORT, 1);

Index: ext/rtree/rtree1.test
==================================================================
--- ext/rtree/rtree1.test
+++ ext/rtree/rtree1.test
@@ -606,8 +606,40 @@
 }
 do_execsql_test 15.2 {
   DROP TABLE t13;
   COMMIT;
 }
+
+# Test cases for the new auxiliary columns feature
+#
+do_catchsql_test 16.100 {
+  CREATE VIRTUAL TABLE t16 USING rtree(id,x0,x1,y0,+aux1,x1);
+} {1 {Auxiliary rtree columns must be last}}
+do_test 16.110 {
+  set sql {
+    CREATE VIRTUAL TABLE t16 USING rtree(
+      id, x00, x01, x10, x11, x20, x21, x30, x31, x40, x41
+  }
+  for {set i 12} {$i<=100} {incr i} {
+     append sql ", +a$i"
+  }
+  append sql ");"
+  execsql $sql
+} {}
+do_test 16.120 {
+  set sql {
+    CREATE VIRTUAL TABLE t16b USING rtree(
+      id, x00, x01, x10, x11, x20, x21, x30, x31, x40, x41
+  }
+  for {set i 12} {$i<=101} {incr i} {
+     append sql ", +a$i"
+  }
+  append sql ");"
+  catchsql $sql
+} {1 {Too many columns for an rtree table}}
+
+
+
+
 
 expand_all_sql db
 finish_test