diff --git a/R/diagnose_design.R b/R/diagnose_design.R
index 3ae02dab..1c58e4b5 100644
--- a/R/diagnose_design.R
+++ b/R/diagnose_design.R
@@ -85,6 +85,9 @@ diagnose_design <- function(...,
     if (is_empty(c("estimator_label", "estimand_label") %icn% simulations_df)) {
       stop("Can't calculate diagnosands on this data.frame, which does not include either an estimator_label or an estimand_label. Did you send a simulations data frame?")
     }
+    if (nrow(simulations_df) == 0) {
+      stop("Can't calculate diagnosands on this data.frame, which has zero rows.")
+    }
     diagnosands <- diagnosands %||% attr(simulations_df, "diagnosands") %||% default_diagnosands
   } else {
     # simulate if needed ------------------------------------------------------
diff --git a/tests/testthat/test-diagnose-design.R b/tests/testthat/test-diagnose-design.R
index 18fb2f42..5ee226d3 100644
--- a/tests/testthat/test-diagnose-design.R
+++ b/tests/testthat/test-diagnose-design.R
@@ -299,3 +299,8 @@ test_that("diagnose_design works when simulations_df lacking parameters attr", {
     
   expect_identical(d1,d2)
 })
+
+
+test_that("diagnose_design stops when a zero-row simulations_df is sent", {
+  expect_error(diagnose_design(data.frame(estimator_label = rep(1, 0))), "which has zero rows")
+})