diff --git a/sf-writer/src/JFH5Writer.cpp b/sf-writer/src/JFH5Writer.cpp
index dcff400..c2407fa 100644
--- a/sf-writer/src/JFH5Writer.cpp
+++ b/sf-writer/src/JFH5Writer.cpp
@@ -136,21 +136,25 @@ void JFH5Writer::write(
         throw runtime_error("Received unexpected block for stop_pulse_id.");
     }
 
-    hsize_t b_i_dims[3] = {n_images_to_copy,
+    hsize_t b_i_dims[3] = {BUFFER_BLOCK_SIZE,
                            MODULE_Y_SIZE * n_modules_,
                            MODULE_X_SIZE};
     H5::DataSpace b_i_space(3, b_i_dims);
+    hsize_t b_i_count[] = {n_images_to_copy,
+                           MODULE_Y_SIZE * n_modules_,
+                           MODULE_X_SIZE};
+    hsize_t b_i_start[] = {n_images_offset, 0, 0};
+    b_i_space.selectHyperslab(H5S_SELECT_SET, b_i_count, b_i_start);
 
     hsize_t f_i_dims[3] = {n_images_,
                            MODULE_Y_SIZE * n_modules_,
                            MODULE_X_SIZE};
     H5::DataSpace f_i_space(3, f_i_dims);
-
-    hsize_t i_count[] = {n_images_to_copy,
-                         MODULE_Y_SIZE * n_modules_,
-                         MODULE_X_SIZE};
-    hsize_t i_start[] = {current_write_index_, 0, 0};
-    f_i_space.selectHyperslab(H5S_SELECT_SET, i_count, i_start);
+    hsize_t f_i_count[] = {n_images_to_copy,
+                           MODULE_Y_SIZE * n_modules_,
+                           MODULE_X_SIZE};
+    hsize_t f_i_start[] = {current_write_index_, 0, 0};
+    f_i_space.selectHyperslab(H5S_SELECT_SET, f_i_count, f_i_start);
 
     image_dataset_.write(
             data, H5::PredType::NATIVE_UINT16, b_i_space, f_i_space);