Index: ext/rtree/rtree.c
==================================================================
--- ext/rtree/rtree.c
+++ ext/rtree/rtree.c
@@ -3650,14 +3650,16 @@
 static sqlite3_stmt *rtreeCheckPrepare(
   RtreeCheck *pCheck,             /* RtreeCheck object */
   const char *zFmt, ...           /* Format string and trailing args */
 ){
   va_list ap;
-  va_start(ap, zFmt);
-  char *z = sqlite3_vmprintf(zFmt, ap);
+  char *z;
   sqlite3_stmt *pRet = 0;
 
+  va_start(ap, zFmt);
+  z = sqlite3_vmprintf(zFmt, ap);
+
   if( pCheck->rc==SQLITE_OK ){
     pCheck->rc = sqlite3_prepare_v2(pCheck->db, z, -1, &pRet, 0);
   }
 
   sqlite3_free(z);