diff --git a/CMakeLists.txt b/CMakeLists.txt
index 95f32fd8ff..2d79a77854 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -154,6 +154,10 @@ set(THREADS "4" CACHE STRING "number of threads to use for external build proces
 set(DEBUG_PORT "/dev/ttyACM0" CACHE STRING "debugging port")
 set(EXTERNAL_MODULES_LOCATION "" CACHE STRING "External modules source location")
 
+if(NOT EXTERNAL_MODULES_LOCATION STREQUAL "")
+	get_filename_component(EXTERNAL_MODULES_LOCATION "${EXTERNAL_MODULES_LOCATION}" ABSOLUTE)
+endif()
+
 #=============================================================================
 # configuration
 #
diff --git a/cmake/common/px4_base.cmake b/cmake/common/px4_base.cmake
index 542dffb0ee..06e5ff4b53 100644
--- a/cmake/common/px4_base.cmake
+++ b/cmake/common/px4_base.cmake
@@ -1041,7 +1041,7 @@ function(px4_generate_parameters_xml)
 
 	add_custom_command(OUTPUT ${OUT}
 		COMMAND ${PYTHON_EXECUTABLE} ${PX4_SOURCE_DIR}/Tools/px_process_params.py
-			-s ${module_list}
+			-s ${module_list} ${EXTERNAL_MODULES_LOCATION}
 			--board CONFIG_ARCH_${BOARD} --xml --inject-xml
 			--overrides ${OVERRIDES}
 		DEPENDS ${param_src_files} ${PX4_SOURCE_DIR}/Tools/px_process_params.py