diff --git a/src/Mod/Assembly/App/AssemblyObject.h b/src/Mod/Assembly/App/AssemblyObject.h
index 8ddf548a42..a5f7df556c 100644
--- a/src/Mod/Assembly/App/AssemblyObject.h
+++ b/src/Mod/Assembly/App/AssemblyObject.h
@@ -33,7 +33,7 @@
 #include <App/PropertyLinks.h>
 #include "SimulationGroup.h"
 
-#include <3rdParty/OndselSolver/OndselSolver/enum.h>
+#include <OndselSolver/enum.h>
 
 namespace MbD
 {
diff --git a/src/Mod/Assembly/App/CMakeLists.txt b/src/Mod/Assembly/App/CMakeLists.txt
index b945f612c1..bf8e14e7ac 100644
--- a/src/Mod/Assembly/App/CMakeLists.txt
+++ b/src/Mod/Assembly/App/CMakeLists.txt
@@ -7,11 +7,6 @@ include_directories(
     ${OCC_INCLUDE_DIR}
     ${PYTHON_INCLUDE_DIRS}
 )
-if (NOT FREECAD_USE_EXTERNAL_ONDSELSOLVER)
-include_directories(
-    ${CMAKE_SOURCE_DIR}/src/3rdParty/OndselSolver
-)
-endif ()
 link_directories(${OCC_LIBRARY_DIR})
 
 set(Assembly_LIBS
diff --git a/src/Mod/Assembly/CMakeLists.txt b/src/Mod/Assembly/CMakeLists.txt
index e74cdbce46..42149923e3 100644
--- a/src/Mod/Assembly/CMakeLists.txt
+++ b/src/Mod/Assembly/CMakeLists.txt
@@ -1,3 +1,14 @@
+if (NOT FREECAD_USE_EXTERNAL_ONDSELSOLVER)
+include_directories(
+    ${CMAKE_SOURCE_DIR}/src/3rdParty/OndselSolver
+)
+else ()
+    check_include_file_cxx(OndselSolver/enum.h HAVE_ONDSELSOLVER_H)
+    if (NOT HAVE_ONDSELSOLVER_H)
+        message(FATAL_ERROR "FREECAD_USE_EXTERNAL_ONDSELSOLVER is set but the required system includes are not available")
+    endif ()
+endif ()
+
 add_subdirectory(App)
 
 if(BUILD_GUI)
diff --git a/tests/src/Mod/Assembly/CMakeLists.txt b/tests/src/Mod/Assembly/CMakeLists.txt
index 1b1d32dc85..5b905d2e9a 100644
--- a/tests/src/Mod/Assembly/CMakeLists.txt
+++ b/tests/src/Mod/Assembly/CMakeLists.txt
@@ -5,6 +5,11 @@ target_include_directories(Assembly_tests_run PUBLIC
     ${Python3_INCLUDE_DIRS}
     ${XercesC_INCLUDE_DIRS}
 )
+if (NOT FREECAD_USE_EXTERNAL_ONDSELSOLVER)
+	target_include_directories(Assembly_tests_run PUBLIC
+		${CMAKE_SOURCE_DIR}/src/3rdParty/OndselSolver
+	)
+endif ()
 target_link_directories(Assembly_tests_run PUBLIC ${OCC_LIBRARY_DIR})
 
 target_link_libraries(Assembly_tests_run