diff --git a/cmake/cpp.cmake b/cmake/cpp.cmake
index 36b6da6352..98c5f5af76 100644
--- a/cmake/cpp.cmake
+++ b/cmake/cpp.cmake
@@ -202,7 +202,7 @@ if(BUILD_MATH_OPT)
   )
   list(APPEND proto_files ${math_opt_proto_files})
 endif()
-if(USE_PDLP)
+if(USE_PDLP OR BUILD_MATH_OPT)
   file(GLOB_RECURSE pdlp_proto_files RELATIVE ${PROJECT_SOURCE_DIR} "ortools/pdlp/*.proto")
   list(APPEND proto_files ${pdlp_proto_files})
 endif()