diff --git a/tools/jfjoch_process.cpp b/tools/jfjoch_process.cpp
index 645b1a62..62343d27 100644
--- a/tools/jfjoch_process.cpp
+++ b/tools/jfjoch_process.cpp
@@ -473,7 +473,7 @@ int main(int argc, char **argv) {
             msg.image = img->image;
             msg.number = current_idx_offset;
             msg.original_number = image_idx;
-            msg.image_collection_efficiency = dataset->efficiency[image_idx];
+            if (dataset->efficiency.size() > image_idx) msg.image_collection_efficiency = dataset->efficiency[image_idx];
 
             total_uncompressed_bytes += msg.image.GetUncompressedSize();