diff --git a/generator/nanopb_generator.py b/generator/nanopb_generator.py
index 3e04215..ca81adf 100644
--- a/generator/nanopb_generator.py
+++ b/generator/nanopb_generator.py
@@ -1,5 +1,5 @@
 '''Generate header file for nanopb from a ProtoBuf FileDescriptorSet.'''
-nanopb_version = "nanopb-0.1.9"
+nanopb_version = "nanopb-0.1.9.1-dev"
 
 try:
     import google.protobuf.descriptor_pb2 as descriptor
diff --git a/pb.h b/pb.h
index daba127..bca3102 100644
--- a/pb.h
+++ b/pb.h
@@ -6,7 +6,7 @@
  * see pb_encode.h or pb_decode.h
  */
 
-#define NANOPB_VERSION nanopb-0.1.9
+#define NANOPB_VERSION nanopb-0.1.9.1-dev
 
 #include <stdint.h>
 #include <stddef.h>