diff --git a/docs/CHANGELOG.txt b/docs/CHANGELOG.txt
index 630a1d81..a979cc8a 100644
--- a/docs/CHANGELOG.txt
+++ b/docs/CHANGELOG.txt
@@ -138,6 +138,7 @@ Other Changes:
 - Tabs: Enforcing minimum size of 1.0f, fixed asserting on zero-tab widths. (#5572)
 - Window: Fixed a potential crash when appending to a child window. (#5515, #3496, #4797) [@rokups]
 - Window: Fixed an issue where uncollapsed a window would show a scrollbar for a frame.
+- Window: Auto-fit size takes account of work rectangle (menu bars eating from viewport). (#5843)
 - IO: Added ImGuiMod_Shortcut which is ImGuiMod_Super on Mac and ImGuiMod_Ctrl otherwise. (#456)
 - IO: Added ImGuiKey_MouseXXX aliases for mouse buttons/wheel so all operations done on ImGuiKey
   can apply to mouse data as well. (#4921)
diff --git a/imgui.cpp b/imgui.cpp
index d5486d64..305a8030 100644
--- a/imgui.cpp
+++ b/imgui.cpp
@@ -5732,8 +5732,7 @@ static ImVec2 CalcWindowAutoFitSize(ImGuiWindow* window, const ImVec2& size_cont
         if (is_popup || is_menu) // Popups and menus bypass style.WindowMinSize by default, but we give then a non-zero minimum size to facilitate understanding problematic cases (e.g. empty popups)
             size_min = ImMin(size_min, ImVec2(4.0f, 4.0f));
 
-        // FIXME-VIEWPORT-WORKAREA: May want to use GetWorkSize() instead of Size depending on the type of windows?
-        ImVec2 avail_size = ImGui::GetMainViewport()->Size;
+        ImVec2 avail_size = ImGui::GetMainViewport()->WorkSize;
         ImVec2 size_auto_fit = ImClamp(size_desired, size_min, ImMax(size_min, avail_size - style.DisplaySafeAreaPadding * 2.0f));
 
         // When the window cannot fit all contents (either because of constraints, either because screen is too small),
diff --git a/imgui.h b/imgui.h
index 5ae2158c..8fa9a65a 100644
--- a/imgui.h
+++ b/imgui.h
@@ -23,7 +23,7 @@
 // Library Version
 // (Integer encoded as XYYZZ for use in #if preprocessor conditionals, e.g. '#if IMGUI_VERSION_NUM > 12345')
 #define IMGUI_VERSION               "1.89 WIP"
-#define IMGUI_VERSION_NUM           18833
+#define IMGUI_VERSION_NUM           18834
 #define IMGUI_HAS_TABLE
 
 /*