diff --git a/R/model_diphtheria.R b/R/model_diphtheria.R
index 26da4c1a..fe234464 100644
--- a/R/model_diphtheria.R
+++ b/R/model_diphtheria.R
@@ -175,6 +175,12 @@ model_diphtheria_cpp <- function(population,
     population_change,
     null.ok = TRUE, len = 2L, types = c("numeric", "list")
   )
+  if (!is.null(population_change)) {
+    checkmate::assert_names(
+      names(population_change),
+      identical.to = c("time", "values")
+    )
+  }
 
   # check the time end and increment
   # restrict increment to lower limit of 1e-6
diff --git a/tests/testthat/test-model_diphtheria.R b/tests/testthat/test-model_diphtheria.R
index b4e7b314..19578469 100644
--- a/tests/testthat/test-model_diphtheria.R
+++ b/tests/testthat/test-model_diphtheria.R
@@ -52,11 +52,11 @@ test_that("Diptheria model, basic expectations", {
   # check for identical numbers of individuals at start and end
   # NOTE: high tolerance because hospitalised compartment is not directly
   # linked to infectious compartment per Finger et al. model structure.
-  # leads to more individuals at final state than initial state
+  # leads to different individuals at final state than initial state
   expect_identical(
     sum(output[output$time == min(output$time), ]$value),
     sum(output[output$time == max(output$time), ]$value),
-    tolerance = 100
+    tolerance = 1e-6
   )
   # check that all age groups in the simulation are the same
   # size as the demography vector