diff --git a/src/DotRecast.Recast.Demo/Tools/TestNavmeshSampleTool.cs b/src/DotRecast.Recast.Demo/Tools/TestNavmeshSampleTool.cs
index 0ecddd9..91d9498 100644
--- a/src/DotRecast.Recast.Demo/Tools/TestNavmeshSampleTool.cs
+++ b/src/DotRecast.Recast.Demo/Tools/TestNavmeshSampleTool.cs
@@ -63,7 +63,7 @@ public class TestNavmeshSampleTool : ISampleTool
     private RcVec3f[] m_queryPoly = new RcVec3f[4];
     private List<RcVec3f> m_smoothPath;
     private DtStatus m_pathFindStatus = DtStatus.DT_FAILURE;
-    private readonly List<RcVec3f> randomPoints = new();
+    private List<RcVec3f> _randomPoints = new();
 
     public TestNavmeshSampleTool()
     {
@@ -552,7 +552,7 @@ public class TestNavmeshSampleTool : ISampleTool
             dd.DepthMask(false);
             dd.Begin(POINTS, 4.0f);
             int col = DuRGBA(64, 16, 0, 220);
-            foreach (RcVec3f point in randomPoints)
+            foreach (RcVec3f point in _randomPoints)
             {
                 dd.Vertex(point.x, point.y + 0.1f, point.z, col);
             }
@@ -766,13 +766,7 @@ public class TestNavmeshSampleTool : ISampleTool
         }
         else if (_mode == RcTestNavmeshToolMode.RANDOM_POINTS_IN_CIRCLE)
         {
-            randomPoints.Clear();
-            if (m_sposSet && m_startRef != 0 && m_eposSet)
-            {
-                var points = new List<RcVec3f>();
-                _tool.FindRandomPointAroundCircle(navQuery, m_startRef, m_spos, m_epos, m_filter, _constrainByCircle, _randomPointCount, ref points);
-                randomPoints.AddRange(points);
-            }
+            _tool.FindRandomPointAroundCircle(navQuery, m_startRef, m_endRef, m_spos, m_epos, m_filter, _constrainByCircle, _randomPointCount, ref _randomPoints);
         }
     }
 
diff --git a/src/DotRecast.Recast.Toolset/Tools/RcTestNavMeshTool.cs b/src/DotRecast.Recast.Toolset/Tools/RcTestNavMeshTool.cs
index 3e1a938..4c65be1 100644
--- a/src/DotRecast.Recast.Toolset/Tools/RcTestNavMeshTool.cs
+++ b/src/DotRecast.Recast.Toolset/Tools/RcTestNavMeshTool.cs
@@ -325,8 +325,14 @@ namespace DotRecast.Recast.Toolset.Tools
             return status;
         }
 
-        public DtStatus FindRandomPointAroundCircle(DtNavMeshQuery navQuery, long startRef, RcVec3f spos, RcVec3f epos, IDtQueryFilter filter, bool constrainByCircle, int count, ref List<RcVec3f> points)
+        public DtStatus FindRandomPointAroundCircle(DtNavMeshQuery navQuery, long startRef, long endRef, RcVec3f spos, RcVec3f epos, IDtQueryFilter filter, bool constrainByCircle, int count,
+            ref List<RcVec3f> points)
         {
+            if (startRef == 0 || endRef == 0)
+            {
+                return DtStatus.DT_FAILURE;
+            }
+
             float dx = epos.x - spos.x;
             float dz = epos.z - spos.z;
             float dist = (float)Math.Sqrt(dx * dx + dz * dz);
@@ -338,6 +344,7 @@ namespace DotRecast.Recast.Toolset.Tools
             var frand = new FRand();
             int prevCnt = points.Count;
 
+            points = new List<RcVec3f>();
             while (0 < count && points.Count < prevCnt + count)
             {
                 var status = navQuery.FindRandomPointAroundCircle(startRef, spos, dist, filter, frand, constraint,