diff --git a/library/CMakeLists.txt b/library/CMakeLists.txt
index a9255ae00..d64b7429f 100644
--- a/library/CMakeLists.txt
+++ b/library/CMakeLists.txt
@@ -264,10 +264,14 @@ FILE(GLOB GENERATE_INPUT_SCRIPTS ${dfapi_SOURCE_DIR}/xml/*.pm ${dfapi_SOURCE_DIR
 FILE(GLOB GENERATE_INPUT_XMLS ${dfapi_SOURCE_DIR}/xml/df.*.xml)
 
 set(CODEGEN_OUT ${dfapi_SOURCE_DIR}/include/df/codegen.out.xml)
-LIST(APPEND CODEGEN_OUT ${GENERATED_HDRS})
+IF(NOT("${CMAKE_GENERATOR}" STREQUAL Ninja))
+    # use BYPRODUCTS instead under Ninja to avoid rebuilds
+    LIST(APPEND CODEGEN_OUT ${GENERATED_HDRS})
+ENDIF()
 
 ADD_CUSTOM_COMMAND(
     OUTPUT ${CODEGEN_OUT}
+    BYPRODUCTS ${GENERATED_HDRS}
     COMMAND ${PERL_EXECUTABLE} ${CMAKE_CURRENT_SOURCE_DIR}/xml/codegen.pl
         ${CMAKE_CURRENT_SOURCE_DIR}/xml
         ${CMAKE_CURRENT_SOURCE_DIR}/include/df