diff --git a/crates/clawhdf5-format/src/filters_blosc2.rs b/crates/clawhdf5-format/src/filters_blosc2.rs
index a70a906..f4d1690 100644
--- a/crates/clawhdf5-format/src/filters_blosc2.rs
+++ b/crates/clawhdf5-format/src/filters_blosc2.rs
@@ -1014,9 +1014,9 @@ impl BlockGeometry<'_> {
         let nd = self.nd;
         unravel(b, self.blocks_in_chunk, &mut p.bidx);
         let mut empty = false;
-        for i in 0..nd.shape.len() {
+        for (i, &c) in cidx.iter().enumerate() {
             let in_chunk = p.bidx[i] * nd.blockshape[i];
-            p.gstart[i] = cidx[i] * nd.chunkshape[i] + in_chunk;
+            p.gstart[i] = c * nd.chunkshape[i] + in_chunk;
             let lim_chunk = nd.chunkshape[i].saturating_sub(in_chunk);
             let lim_shape = nd.shape[i].saturating_sub(p.gstart[i]);
             p.valid[i] = nd.blockshape[i].min(lim_chunk).min(lim_shape);