diff --git a/pkg/nanopb/Makefile.gensrc b/pkg/nanopb/Makefile.gensrc
index c0803df6c5..1c86af590c 100644
--- a/pkg/nanopb/Makefile.gensrc
+++ b/pkg/nanopb/Makefile.gensrc
@@ -16,7 +16,7 @@ PROTO_INCLUDES += -I.
 PROTO_INCLUDES += -I$(PKGDIRBASE)/nanopb/generator/proto
 PROTO_INCLUDES += -I$(PROTOBUF_PATH)
 
-$(SRC): $(GENSRC)
+$(SRC) $(SRCXX): $(GENSRC)
 
 $(GENSRC): $(PROTOBUF_FILES)
 	$(Q)D=$(BINDIR)/$(MODULE) && \