diff --git a/imgui.cpp b/imgui.cpp
index c731909f..f2c88e4c 100644
--- a/imgui.cpp
+++ b/imgui.cpp
@@ -3192,7 +3192,7 @@ static void ClosePopup(ImGuiID id)
     if (!IsPopupOpen(id))
         return;
     ImGuiState& g = *GImGui;
-    ClosePopupToLevel(g.OpenedPopupStack.size() - 1);
+    ClosePopupToLevel((int)g.OpenedPopupStack.size() - 1);
 }
 
 // Close the popup we have begin-ed into.