diff --git a/CMakeLists.txt b/CMakeLists.txt
index 63ada4df..760a207b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -79,3 +79,36 @@ if(_m5gfx_arduino_enabled)
         target_link_libraries(${COMPONENT_LIB} PUBLIC ${_m5gfx_arduino_lib})
     endif()
 endif()
+
+# Panel_LT8912B (the PoE-P4 display output board) talks to the bridge through M5Unified's I2C_Class, which it
+# picks up with __has_include(<utility/I2C_Class.hpp>). In an ESP-IDF build that header is only
+# visible when this library is given M5Unified's source directory, so add it whenever an
+# M5Unified component is part of the build (headers only; the symbols resolve at link time as
+# the component libraries are linked as one group).
+#   M5GFX_M5UNIFIED_COMPONENT=<name>  use a differently named M5Unified component
+#   M5GFX_M5UNIFIED_COMPONENT=OFF     disable the automatic include path
+set(_m5gfx_m5unified_candidates M5Unified m5unified m5stack__m5unified)
+set(_m5gfx_m5unified_enabled ON)
+if(DEFINED M5GFX_M5UNIFIED_COMPONENT AND NOT "${M5GFX_M5UNIFIED_COMPONENT}" STREQUAL "")
+    if(M5GFX_M5UNIFIED_COMPONENT)
+        set(_m5gfx_m5unified_candidates ${M5GFX_M5UNIFIED_COMPONENT})
+    else()
+        set(_m5gfx_m5unified_enabled OFF)
+    endif()
+endif()
+if(_m5gfx_m5unified_enabled)
+    idf_build_get_property(_m5gfx_m5unified_build_components BUILD_COMPONENTS)
+    set(_m5gfx_m5unified_hits)
+    foreach(_m5gfx_m5unified_name ${_m5gfx_m5unified_candidates})
+        if(_m5gfx_m5unified_name IN_LIST _m5gfx_m5unified_build_components)
+            list(APPEND _m5gfx_m5unified_hits ${_m5gfx_m5unified_name})
+        endif()
+    endforeach()
+    list(LENGTH _m5gfx_m5unified_hits _m5gfx_m5unified_count)
+    if(_m5gfx_m5unified_count GREATER 1)
+        message(FATAL_ERROR "M5GFX: several M5Unified components are in the build (${_m5gfx_m5unified_hits}). Set M5GFX_M5UNIFIED_COMPONENT to the one to use.")
+    elseif(_m5gfx_m5unified_count EQUAL 1)
+        idf_component_get_property(_m5gfx_m5unified_dir ${_m5gfx_m5unified_hits} COMPONENT_DIR)
+        target_include_directories(${COMPONENT_LIB} PRIVATE ${_m5gfx_m5unified_dir}/src)
+    endif()
+endif()