diff --git a/src/fileformat.proto b/src/fileformat.proto
index 89a56da..696b483 100644
--- a/src/fileformat.proto
+++ b/src/fileformat.proto
@@ -8,7 +8,8 @@ THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLI
 
 */
 
-//option optimize_for = LITE_RUNTIME;
+syntax = "proto2";
+
 option java_package = "crosby.binary";
 package OSMPBF;
 
diff --git a/src/osmformat.proto b/src/osmformat.proto
index 05425e8..a5d3b27 100644
--- a/src/osmformat.proto
+++ b/src/osmformat.proto
@@ -8,7 +8,8 @@ THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLI
 
 */
 
-//option optimize_for = LITE_RUNTIME;
+syntax = "proto2";
+
 option java_package = "crosby.binary";
 package OSMPBF;