diff --git a/mlir/include/mlir/Dialect/SparseTensor/Utils/Merger.h b/mlir/include/mlir/Dialect/SparseTensor/Utils/Merger.h
--- a/mlir/include/mlir/Dialect/SparseTensor/Utils/Merger.h
+++ b/mlir/include/mlir/Dialect/SparseTensor/Utils/Merger.h
@@ -432,8 +432,15 @@
   /// Sets the level number and level-type of the `t`th tensor on
   /// `i`th loop.
   void setLevelAndType(TensorId t, LoopId i, Level lvl, DimLevelType dlt) {
-    assert(t < numTensors && i < numLoops && lvl < lvlToLoop[t].size() &&
-           isValidDLT(dlt));
+    assert(t < numTensors && i < numLoops && isValidDLT(dlt));
+    // In case with indexing map like (d0) -> (0, d0), there might be more
+    // levels then loops because of the constant index.
+    // TODO: Constant indices are currently not support on sparse tensor, but
+    // are allowed in non-annotated dense tensor. Support it, it would be
+    // required for sparse tensor slice rank reducing too.
+    if (lvl >= lvlToLoop[t].size())
+      lvlToLoop[t].resize(lvl + 1);
+
     lvlTypes[t][i] = dlt;
     loopToLvl[t][i] = lvl;
     lvlToLoop[t][lvl] = i;