diff --git a/apis/r/R/write_soma.R b/apis/r/R/write_soma.R
index e1433458d6..44eabe3b4e 100644
--- a/apis/r/R/write_soma.R
+++ b/apis/r/R/write_soma.R
@@ -219,12 +219,32 @@ write_soma.data.frame <- function(
     choices = names(x),
     several.ok = TRUE
   )
+
+  # For index_column_name being soma_joinid -- this being the default
+  # -- set that domain slot to match the date. This will endow the
+  # dataframe with something users think of as a "shape". For the
+  # other slots, set the domain wide open.
+  #
+  domain <- NULL
+  if (.new_shape_feature_flag_is_enabled()) {
+    domain <- list()
+    for (index_column_name in index_column_names) {
+      if (index_column_name == "soma_joinid") {
+        domain[["soma_joinid"]] <- c(0, nrow(x) - 1)
+      } else {
+        domain[[index_column_name]] <- NULL
+      }
+    }
+  }
+
   # Create the SOMADataFrame
   tbl <- arrow::arrow_table(x)
   sdf <- SOMADataFrameCreate(
     uri = uri,
     schema = tbl$schema,
     index_column_names = index_column_names,
+    # XXX TEMP
+    domain = domain,
     ingest_mode = ingest_mode,
     platform_config = platform_config,
     tiledbsoma_ctx = tiledbsoma_ctx
diff --git a/apis/r/tests/testthat/test-write-soma-resume.R b/apis/r/tests/testthat/test-write-soma-resume.R
index 4a2aaf517c..7b55a5449a 100644
--- a/apis/r/tests/testthat/test-write-soma-resume.R
+++ b/apis/r/tests/testthat/test-write-soma-resume.R
@@ -164,6 +164,7 @@ test_that("Resume-mode data frames", {
     }
   }
 
+  # TODO: resize if new shape feature-flag is enabled
   expect_s3_class(
     sdfc <- write_soma(
       co2,