diff --git a/backends/imgui_impl_marmalade.cpp b/backends/imgui_impl_marmalade.cpp
index aa6b32067..6e9b8f803 100644
--- a/backends/imgui_impl_marmalade.cpp
+++ b/backends/imgui_impl_marmalade.cpp
@@ -6,13 +6,14 @@
 // Missing features:
 //  [ ] Renderer: Clipping rectangles are not honored.
 
-// You can use unmodified imgui_impl_* files in your project. See examples/ folder for examples of using this. 
+// You can use unmodified imgui_impl_* files in your project. See examples/ folder for examples of using this.
 // Prefer including the entire imgui/ repository into your project (either as a copy or as a submodule), and only build the backends you need.
 // If you are new to Dear ImGui, read documentation from the docs/ folder + read the top of imgui.cpp.
 // Read online: https://github.com/ocornut/imgui/tree/master/docs
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  2021-12-08: Renderer: Fixed mishandling of the the ImDrawCmd::IdxOffset field! This is an old bug but it never had an effect until some internal rendering changes in 1.86.
 //  2021-05-19: Renderer: Replaced direct access to ImDrawCmd::TextureId with a call to ImDrawCmd::GetTexID(). (will become a requirement)
 //  2019-07-21: Inputs: Added mapping for ImGuiKey_KeyPadEnter.
 //  2019-05-11: Inputs: Don't filter value from character callback before calling AddInputCharacter().
@@ -91,9 +92,8 @@ void ImGui_Marmalade_RenderDrawData(ImDrawData* draw_data)
                 pCurrentMaterial->SetAlphaTestMode(CIwMaterial::ALPHATEST_DISABLED);
                 pCurrentMaterial->SetTexture((CIwTexture*)pcmd->GetTexID());
                 IwGxSetMaterial(pCurrentMaterial);
-                IwGxDrawPrims(IW_GX_TRI_LIST, (uint16*)idx_buffer, pcmd->ElemCount);
+                IwGxDrawPrims(IW_GX_TRI_LIST, (uint16*)(idx_buffer + pcmd->IdxOffset), pcmd->ElemCount);
             }
-            idx_buffer += pcmd->ElemCount;
         }
         IwGxFlush();
     }
diff --git a/backends/imgui_impl_opengl2.cpp b/backends/imgui_impl_opengl2.cpp
index 65e778f55..17a6faebb 100644
--- a/backends/imgui_impl_opengl2.cpp
+++ b/backends/imgui_impl_opengl2.cpp
@@ -19,6 +19,7 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  2021-12-08: OpenGL: Fixed mishandling of the the ImDrawCmd::IdxOffset field! This is an old bug but it never had an effect until some internal rendering changes in 1.86.
 //  2021-06-29: Reorganized backend to pull data from a single structure to facilitate usage with multiple-contexts (all g_XXXX access changed to bd->XXXX).
 //  2021-05-19: OpenGL: Replaced direct access to ImDrawCmd::TextureId with a call to ImDrawCmd::GetTexID(). (will become a requirement)
 //  2021-01-03: OpenGL: Backup, setup and restore GL_SHADE_MODEL state, disable GL_STENCIL_TEST and disable GL_NORMAL_ARRAY client state to increase compatibility with legacy OpenGL applications.
@@ -211,9 +212,8 @@ void ImGui_ImplOpenGL2_RenderDrawData(ImDrawData* draw_data)
 
                 // Bind texture, Draw
                 glBindTexture(GL_TEXTURE_2D, (GLuint)(intptr_t)pcmd->GetTexID());
-                glDrawElements(GL_TRIANGLES, (GLsizei)pcmd->ElemCount, sizeof(ImDrawIdx) == 2 ? GL_UNSIGNED_SHORT : GL_UNSIGNED_INT, idx_buffer);
+                glDrawElements(GL_TRIANGLES, (GLsizei)pcmd->ElemCount, sizeof(ImDrawIdx) == 2 ? GL_UNSIGNED_SHORT : GL_UNSIGNED_INT, idx_buffer + pcmd->IdxOffset);
             }
-            idx_buffer += pcmd->ElemCount;
         }
     }
 
diff --git a/docs/CHANGELOG.txt b/docs/CHANGELOG.txt
index 3a9b36a02..9aa7f2b42 100644
--- a/docs/CHANGELOG.txt
+++ b/docs/CHANGELOG.txt
@@ -90,6 +90,9 @@ Other Changes:
 - Backends: Vulkan: Call vkCmdSetScissor() at the end of render with a full-viewport to reduce
   likehood of issues with people using VK_DYNAMIC_STATE_SCISSOR in their app without calling
   vkCmdSetScissor() explicitly every frame. (#4644)
+- Backends: OpenGL2, Marmalade: Fixed mishandling of the ImDrawCmd::IdxOffset field. This is an old bug,
+  but due to the way we created drawlists, it never had any visible side-effect before.
+  The new code for handling Modal and CTRL+Tab dimming/whitening recently made the bug surface. (#4790)
 - Backends: DX12: Fixed DRAW_EMPTY_SCISSOR_RECTANGLE warnings. (#4775)
 - Backends: SDL_Renderer: Added support for large meshes (64k+ vertices) with 16-bit indices,
   enabling 'ImGuiBackendFlags_RendererHasVtxOffset' in the backend. (#3926) [@rokups]