diff --git a/imgui.cpp b/imgui.cpp
index 139258d99..fa09a1391 100644
--- a/imgui.cpp
+++ b/imgui.cpp
@@ -7022,8 +7022,8 @@ void ImDrawList::Stroke(ImU32 col, bool closed)
 void ImDrawList::Rect(const ImVec2& a, const ImVec2& b, float rounding, int rounding_corners)
 {
     float r = rounding;
-    r = ImMin(r, fabsf(b.x-a.x) * ( ((rounding_corners&(1|2))==(1|2)) || ((rounding_corners&(4|8))==(4|8)) ? 0.5f : 1.0f ));
-    r = ImMin(r, fabsf(b.y-a.y) * ( ((rounding_corners&(1|8))==(1|8)) || ((rounding_corners&(2|4))==(2|4)) ? 0.5f : 1.0f ));
+    r = ImMin(r, fabsf(b.x-a.x) * ( ((rounding_corners&(1|2))==(1|2)) || ((rounding_corners&(4|8))==(4|8)) ? 0.5f : 1.0f ) - 1.0f);
+    r = ImMin(r, fabsf(b.y-a.y) * ( ((rounding_corners&(1|8))==(1|8)) || ((rounding_corners&(2|4))==(2|4)) ? 0.5f : 1.0f ) - 1.0f);
 
     if (r == 0.0f || rounding_corners == 0)
     {