diff --git a/sf-writer/sf_h5_writer.cpp b/sf-writer/sf_h5_writer.cpp
index d7baf8b..357e7a4 100644
--- a/sf-writer/sf_h5_writer.cpp
+++ b/sf-writer/sf_h5_writer.cpp
@@ -26,8 +26,8 @@ int main (int argc, char *argv[])
 
     string root_folder = string(argv[1]);
     string output_file = string(argv[2]);
-    uint64_t start_pulse_id = (uint64_t) atoi(argv[3]);
-    uint64_t stop_pulse_id = (uint64_t) atoi(argv[4]);
+    uint64_t start_pulse_id = (uint64_t) atoll(argv[3]);
+    uint64_t stop_pulse_id = (uint64_t) atoll(argv[4]);
 
     BufferMultiReader reader(root_folder);
     UdpFrameMetadata metadata;