diff --git a/R/pred.R b/R/pred.R
index d3bcf3f..b87274a 100644
--- a/R/pred.R
+++ b/R/pred.R
@@ -413,6 +413,15 @@ pred_fun_Y <- function(model, yrestrictions, outcome_type, outcome_name,
     # Fit GLM for outcome variable using user-specified model and entire dataset
     fitY <- stats::glm(model, family = outcome_fam, data = obs_data, y = TRUE)
   }
+  if(anyNA(coefficients(fitY))) {
+    stop(
+      "`NA` coefficients produced in prediction model. ",
+      "This may be due to (multi)collinearity in `ymodel` predictor variables, ",
+      "or including `time_name` variable in a 'continuous_eof' model.\n",
+      "Variables returning `NA` coefficients:\n - ",
+      paste(names(coefficients(fitY)[is.na(coefficients(fitY))]), collapse = "\n - ")
+      )
+  }
   fitY$rmse <- add_rmse(fitY)
   fitY$stderr <- add_stderr(fitY)
   fitY$vcov <- add_vcov(fitY)
diff --git a/R/simulate.R b/R/simulate.R
index 4042707..07d8c31 100644
--- a/R/simulate.R
+++ b/R/simulate.R
@@ -145,6 +145,28 @@ simulate <- function(o, fitcov, fitY, fitD,
                      min_time, show_progress, pb, int_visit_type, ...){
   set.seed(subseed)
 
+  invalid_coefs <- vapply(lapply(fitcov, coefficients), anyNA, logical(1)) |> any()
+
+  if (invalid_coefs) {
+
+    coefficients <- lapply(fitcov, coefficients)
+
+    errored_parts <- coefficients[vapply(coefficients, anyNA, logical(1))]  |>
+      lapply(\(coefs) {names(coefs[is.na(coefs)])})
+
+
+    paste(names(errored_parts), errored_parts, sep = "\n - ", collapse = "\n\n")
+
+    stop(
+        "`NA` coefficients produced in covariate prediction model. ",
+        "This may be due to (multi)collinearity in `covmodels` predictor variables, ",
+        "or including `time_name` variable in a 'continuous_eof' model.\n",
+        "Variables returning `NA` coefficients:\n",
+        paste(names(errored_parts), errored_parts, sep = "\n - ", collapse = "\n\n")
+    )
+
+  }
+
   # Mechanism of passing intervention variable and intervention is different for parallel
   # and non-parallel versions
   if (parallel){