diff --git a/imgui.cpp b/imgui.cpp
index cee33f50..318d3373 100644
--- a/imgui.cpp
+++ b/imgui.cpp
@@ -4466,23 +4466,23 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
 
         // Calculate auto-fit size, handle automatic resize
         const ImVec2 size_auto_fit = CalcSizeAutoFit(window);
-        ImVec2 size_for_scrollbars_visibility = window->SizeFullAtLastBegin;
+        ImVec2 size_full_modified(FLT_MAX, FLT_MAX);
         if (flags & ImGuiWindowFlags_AlwaysAutoResize && !window->Collapsed)
         {
             // Using SetNextWindowSize() overrides ImGuiWindowFlags_AlwaysAutoResize, so it can be used on tooltips/popups, etc.
             if (!window_size_x_set_by_api)
-                window->SizeFull.x = size_for_scrollbars_visibility.x = size_auto_fit.x;
+                window->SizeFull.x = size_full_modified.x = size_auto_fit.x;
             if (!window_size_y_set_by_api)
-                window->SizeFull.y = size_for_scrollbars_visibility.y = size_auto_fit.y;
+                window->SizeFull.y = size_full_modified.y = size_auto_fit.y;
         }
         else if (window->AutoFitFramesX > 0 || window->AutoFitFramesY > 0)
         {
             // Auto-fit only grows during the first few frames
             // We still process initial auto-fit on collapsed windows to get a window width, but otherwise don't honor ImGuiWindowFlags_AlwaysAutoResize ImGuiWindowFlags_AlwaysAutoResize.
             if (!window_size_x_set_by_api && window->AutoFitFramesX > 0)
-                window->SizeFull.x = size_for_scrollbars_visibility.x = window->AutoFitOnlyGrows ? ImMax(window->SizeFull.x, size_auto_fit.x) : size_auto_fit.x;
+                window->SizeFull.x = size_full_modified.x = window->AutoFitOnlyGrows ? ImMax(window->SizeFull.x, size_auto_fit.x) : size_auto_fit.x;
             if (!window_size_y_set_by_api && window->AutoFitFramesY > 0)
-                window->SizeFull.y = size_for_scrollbars_visibility.y = window->AutoFitOnlyGrows ? ImMax(window->SizeFull.y, size_auto_fit.y) : size_auto_fit.y;
+                window->SizeFull.y = size_full_modified.y = window->AutoFitOnlyGrows ? ImMax(window->SizeFull.y, size_auto_fit.y) : size_auto_fit.y;
             if (!window->Collapsed)
                 MarkIniSettingsDirty(window);
         }
@@ -4501,10 +4501,13 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
         // Update scrollbar status (based on the Size that was effective during last frame or the auto-resized Size). 
         if (!window->Collapsed)
         {
-            window->ScrollbarY = (flags & ImGuiWindowFlags_AlwaysVerticalScrollbar) || ((window->SizeContents.y > size_for_scrollbars_visibility.y) && !(flags & ImGuiWindowFlags_NoScrollbar));
-            window->ScrollbarX = (flags & ImGuiWindowFlags_AlwaysHorizontalScrollbar) || ((window->SizeContents.x > size_for_scrollbars_visibility.x - (window->ScrollbarY ? style.ScrollbarSize : 0.0f) - window->WindowPadding.x) && !(flags & ImGuiWindowFlags_NoScrollbar) && (flags & ImGuiWindowFlags_HorizontalScrollbar));
+            // When reading the current size we need to read it after size constraints have been applied
+            float size_x_for_scrollbars = size_full_modified.x != FLT_MAX ? window->SizeFull.x : window->SizeFullAtLastBegin.x;
+            float size_y_for_scrollbars = size_full_modified.y != FLT_MAX ? window->SizeFull.y : window->SizeFullAtLastBegin.y;
+            window->ScrollbarY = (flags & ImGuiWindowFlags_AlwaysVerticalScrollbar) || ((window->SizeContents.y > size_y_for_scrollbars) && !(flags & ImGuiWindowFlags_NoScrollbar));
+            window->ScrollbarX = (flags & ImGuiWindowFlags_AlwaysHorizontalScrollbar) || ((window->SizeContents.x > size_x_for_scrollbars - (window->ScrollbarY ? style.ScrollbarSize : 0.0f) - window->WindowPadding.x) && !(flags & ImGuiWindowFlags_NoScrollbar) && (flags & ImGuiWindowFlags_HorizontalScrollbar));
             if (window->ScrollbarX && !window->ScrollbarY)
-                window->ScrollbarY = (window->SizeContents.y > size_for_scrollbars_visibility.y + style.ScrollbarSize) && !(flags & ImGuiWindowFlags_NoScrollbar);
+                window->ScrollbarY = (window->SizeContents.y > size_y_for_scrollbars + style.ScrollbarSize) && !(flags & ImGuiWindowFlags_NoScrollbar);
             window->ScrollbarSizes = ImVec2(window->ScrollbarY ? style.ScrollbarSize : 0.0f, window->ScrollbarX ? style.ScrollbarSize : 0.0f);
         }