diff --git a/CMakeLists.txt b/CMakeLists.txt
index 9141422bd5a..29458bf13aa 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -242,7 +242,7 @@ add_external_subdirectory(nanopb)
 
 target_compile_definitions(
   protobuf-nanopb-static PUBLIC
-  -DPB_FIELD_32BIT -DPB_ENABLE_MALLOC
+  -DPB_FIELD_32BIT -DPB_ENABLE_MALLOC -DPB_NO_PACKED_STRUCTS=1
 )
 
 # Enable #include <nanopb/pb.h>