diff --git a/src/CircleTool.cpp b/src/CircleTool.cpp
index 50dccfc..d8b18f8 100644
--- a/src/CircleTool.cpp
+++ b/src/CircleTool.cpp
@@ -17,7 +17,9 @@ CircleTool::CircleTool(ViewportWidget* viewport)
 void CircleTool::activate()
 {
     SketchTool::activate();
+    m_dimensionModes.clear();
     m_dimensionModes << "diameter";
+    m_dimensionPropertyNames.clear();
     m_dimensionPropertyNames["diameter"] = "diameterInput";
 
     m_viewport->setProperty("diameterInput", "");