diff --git a/cmake/Modules/compdb.cmake b/cmake/Modules/compdb.cmake
index a169208..ddf8e1e 100644
--- a/cmake/Modules/compdb.cmake
+++ b/cmake/Modules/compdb.cmake
@@ -10,14 +10,16 @@ find_program(COMPDB_PATH
   )
 
 
+if(CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR)
 
-if (COMPDB_PATH)
-  IF(NOT TARGET COMPD)
-    add_custom_target(COMPD
-      ALL
-      DEPENDS ${CMAKE_CURRENT_BINARY_DIR}/compile_commands.json
-      WORKING_DIRECTORY ${CMAKE_SOURCE_DIR}
-      COMMAND ${COMPDB_PATH} -p ${CMAKE_CURRENT_BINARY_DIR} list >compile_commands.json
-    )
+  if (COMPDB_PATH)
+    IF(NOT TARGET COMPD)
+      add_custom_target(COMPD
+        ALL
+        DEPENDS ${CMAKE_CURRENT_BINARY_DIR}/compile_commands.json
+        WORKING_DIRECTORY ${CMAKE_SOURCE_DIR}
+        COMMAND ${COMPDB_PATH} -p ${CMAKE_CURRENT_BINARY_DIR} list >compile_commands.json
+      )
+    endif()
   endif()
 endif()