diff --git a/R/check_model_diagnostics.R b/R/check_model_diagnostics.R
index 431a2bc0f..8897c685e 100644
--- a/R/check_model_diagnostics.R
+++ b/R/check_model_diagnostics.R
@@ -460,7 +460,7 @@
   if (!is.na(match(faminfo$family, c("binomial", "poisson", "truncated_poisson")))) {
     return(1)
   }
-  betad <- model$fit$par["betad"]
+  betad <- model$fit$par["betadisp"]
   switch(faminfo$family,
     gaussian = exp(0.5 * betad),
     Gamma = exp(-0.5 * betad),
diff --git a/tests/testthat/test-check_singularity.R b/tests/testthat/test-check_singularity.R
index dc0d56964..8a07b85e0 100644
--- a/tests/testthat/test-check_singularity.R
+++ b/tests/testthat/test-check_singularity.R
@@ -29,7 +29,7 @@ test_that("check_singularity", {
     newparam = list(
       beta = 0,
       theta = rep(0, 21),
-      betad = 0
+      betadisp = 0
     )
   )[[1]]
   expect_warning(expect_warning({