diff --git a/NEWS.md b/NEWS.md
index b7f4641b7..b46487f17 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -47,6 +47,8 @@
 
 * The quantile regression prediction type was disabled for the deprecated `surv_reg()` model. 
 
+* `NULL` is no longer accepted as an engine (#1242).
+
 
 # parsnip 1.2.1
 
diff --git a/R/engines.R b/R/engines.R
index fceea94eb..86e3ffd87 100644
--- a/R/engines.R
+++ b/R/engines.R
@@ -111,7 +111,7 @@ set_engine <- function(object, engine, ...) {
 set_engine.model_spec <- function(object, engine, ...) {
   mod_type <- class(object)[1]
 
-  if (rlang::is_missing(engine)) {
+  if (rlang::is_missing(engine) || is.null(engine)) {
     stop_missing_engine(mod_type, call = caller_env(0))
   }
   object$engine <- engine
diff --git a/man/details_linear_reg_glmer.Rd b/man/details_linear_reg_glmer.Rd
index 67d8745bb..d4da1c9a4 100644
--- a/man/details_linear_reg_glmer.Rd
+++ b/man/details_linear_reg_glmer.Rd
@@ -52,7 +52,7 @@ linear predictor (\verb{\eta}) for a random intercept:
 \if{html}{\out{<div class="sourceCode">}}\preformatted{\eta_\{i\} = (\beta_0 + b_\{0i\}) + \beta_1x_\{i1\}
 }\if{html}{\out{</div>}}
 
-where $i$ denotes the \code{i}th independent experimental unit
+where \code{i} denotes the \code{i}th independent experimental unit
 (e.g. subject). When the model has seen subject \code{i}, it can use that
 subject’s data to adjust the \emph{population} intercept to be more specific
 to that subjects results.
diff --git a/man/details_linear_reg_lmer.Rd b/man/details_linear_reg_lmer.Rd
index 0441f464a..4e4b5a34d 100644
--- a/man/details_linear_reg_lmer.Rd
+++ b/man/details_linear_reg_lmer.Rd
@@ -44,7 +44,7 @@ linear predictor (\verb{\eta}) for a random intercept:
 \if{html}{\out{<div class="sourceCode">}}\preformatted{\eta_\{i\} = (\beta_0 + b_\{0i\}) + \beta_1x_\{i1\}
 }\if{html}{\out{</div>}}
 
-where $i$ denotes the \code{i}th independent experimental unit
+where \code{i} denotes the \code{i}th independent experimental unit
 (e.g. subject). When the model has seen subject \code{i}, it can use that
 subject’s data to adjust the \emph{population} intercept to be more specific
 to that subjects results.
diff --git a/man/details_linear_reg_stan_glmer.Rd b/man/details_linear_reg_stan_glmer.Rd
index 3bcb67ddf..78132f4bb 100644
--- a/man/details_linear_reg_stan_glmer.Rd
+++ b/man/details_linear_reg_stan_glmer.Rd
@@ -64,7 +64,7 @@ linear predictor (\verb{\eta}) for a random intercept:
 \if{html}{\out{<div class="sourceCode">}}\preformatted{\eta_\{i\} = (\beta_0 + b_\{0i\}) + \beta_1x_\{i1\}
 }\if{html}{\out{</div>}}
 
-where $i$ denotes the \code{i}th independent experimental unit
+where \code{i} denotes the \code{i}th independent experimental unit
 (e.g. subject). When the model has seen subject \code{i}, it can use that
 subject’s data to adjust the \emph{population} intercept to be more specific
 to that subjects results.
diff --git a/man/details_logistic_reg_glmer.Rd b/man/details_logistic_reg_glmer.Rd
index b848df19c..a87a9e9c6 100644
--- a/man/details_logistic_reg_glmer.Rd
+++ b/man/details_logistic_reg_glmer.Rd
@@ -44,7 +44,7 @@ linear predictor (\verb{\eta}) for a random intercept:
 \if{html}{\out{<div class="sourceCode">}}\preformatted{\eta_\{i\} = (\beta_0 + b_\{0i\}) + \beta_1x_\{i1\}
 }\if{html}{\out{</div>}}
 
-where $i$ denotes the \code{i}th independent experimental unit
+where \code{i} denotes the \code{i}th independent experimental unit
 (e.g. subject). When the model has seen subject \code{i}, it can use that
 subject’s data to adjust the \emph{population} intercept to be more specific
 to that subjects results.
diff --git a/man/details_logistic_reg_stan_glmer.Rd b/man/details_logistic_reg_stan_glmer.Rd
index ce1281501..628702e45 100644
--- a/man/details_logistic_reg_stan_glmer.Rd
+++ b/man/details_logistic_reg_stan_glmer.Rd
@@ -63,7 +63,7 @@ linear predictor (\verb{\eta}) for a random intercept:
 \if{html}{\out{<div class="sourceCode">}}\preformatted{\eta_\{i\} = (\beta_0 + b_\{0i\}) + \beta_1x_\{i1\}
 }\if{html}{\out{</div>}}
 
-where $i$ denotes the \code{i}th independent experimental unit
+where \code{i} denotes the \code{i}th independent experimental unit
 (e.g. subject). When the model has seen subject \code{i}, it can use that
 subject’s data to adjust the \emph{population} intercept to be more specific
 to that subjects results.
diff --git a/man/details_poisson_reg_glmer.Rd b/man/details_poisson_reg_glmer.Rd
index 5a32c17bd..520798925 100644
--- a/man/details_poisson_reg_glmer.Rd
+++ b/man/details_poisson_reg_glmer.Rd
@@ -44,7 +44,7 @@ linear predictor (\verb{\eta}) for a random intercept:
 \if{html}{\out{<div class="sourceCode">}}\preformatted{\eta_\{i\} = (\beta_0 + b_\{0i\}) + \beta_1x_\{i1\}
 }\if{html}{\out{</div>}}
 
-where $i$ denotes the \code{i}th independent experimental unit
+where \code{i} denotes the \code{i}th independent experimental unit
 (e.g. subject). When the model has seen subject \code{i}, it can use that
 subject’s data to adjust the \emph{population} intercept to be more specific
 to that subjects results.
diff --git a/man/details_poisson_reg_stan_glmer.Rd b/man/details_poisson_reg_stan_glmer.Rd
index ef1065ada..e34078846 100644
--- a/man/details_poisson_reg_stan_glmer.Rd
+++ b/man/details_poisson_reg_stan_glmer.Rd
@@ -63,7 +63,7 @@ linear predictor (\verb{\eta}) for a random intercept:
 \if{html}{\out{<div class="sourceCode">}}\preformatted{\eta_\{i\} = (\beta_0 + b_\{0i\}) + \beta_1x_\{i1\}
 }\if{html}{\out{</div>}}
 
-where $i$ denotes the \code{i}th independent experimental unit
+where \code{i} denotes the \code{i}th independent experimental unit
 (e.g. subject). When the model has seen subject \code{i}, it can use that
 subject’s data to adjust the \emph{population} intercept to be more specific
 to that subjects results.
diff --git a/man/parsnip-package.Rd b/man/parsnip-package.Rd
index 84b9a622d..2e074dc3b 100644
--- a/man/parsnip-package.Rd
+++ b/man/parsnip-package.Rd
@@ -30,7 +30,7 @@ Authors:
 Other contributors:
 \itemize{
   \item Emil Hvitfeldt \email{emil.hvitfeldt@posit.co} [contributor]
-  \item Posit Software, PBC [copyright holder, funder]
+  \item Posit Software, PBC (03wc8by49) [copyright holder, funder]
 }
 
 }
diff --git a/tests/testthat/_snaps/engines.md b/tests/testthat/_snaps/engines.md
new file mode 100644
index 000000000..dd1342c9c
--- /dev/null
+++ b/tests/testthat/_snaps/engines.md
@@ -0,0 +1,8 @@
+# NULL engines
+
+    Code
+      set_engine(nearest_neighbor(), NULL)
+    Condition
+      Error in `set_engine()`:
+      ! Missing engine. Possible mode/engine combinations are: classification {kknn} and regression {kknn}.
+
diff --git a/tests/testthat/_snaps/mlp_keras.md b/tests/testthat/_snaps/mlp_keras.md
index bf9652e57..02479ada2 100644
--- a/tests/testthat/_snaps/mlp_keras.md
+++ b/tests/testthat/_snaps/mlp_keras.md
@@ -14,5 +14,4 @@
         Class ~ A + B, data = modeldata::two_class_dat)
     Condition
       Error in `parsnip::keras_mlp()`:
-      ! `activation` should be one of: elu, exponential, gelu, hardsigmoid, linear, relu, selu, sigmoid, softmax, softplus, softsign, swish, and tanh, not "invalid".
-
+      ! `activation` should be one of: elu, exponential, gelu, hard_sigmoid, linear, relu, selu, sigmoid, softmax, softplus, softsign, swish, and tanh, not "invalid".
\ No newline at end of file
diff --git a/tests/testthat/_snaps/rand_forest.md b/tests/testthat/_snaps/rand_forest.md
index fc233adc6..7265dcc6a 100644
--- a/tests/testthat/_snaps/rand_forest.md
+++ b/tests/testthat/_snaps/rand_forest.md
@@ -19,8 +19,9 @@
 
     Code
       res <- translate(rand_forest(mode = "classification") %>% set_engine(NULL))
-    Message
-      Used `engine = 'ranger'` for translation.
+    Condition
+      Error in `set_engine()`:
+      ! Missing engine. Possible mode/engine combinations are: classification {ranger, randomForest, spark} and regression {ranger, randomForest, spark}.
 
 ---
 
diff --git a/tests/testthat/_snaps/surv_reg.md b/tests/testthat/_snaps/surv_reg.md
index 66039a420..9a2ae9610 100644
--- a/tests/testthat/_snaps/surv_reg.md
+++ b/tests/testthat/_snaps/surv_reg.md
@@ -32,8 +32,9 @@
 
     Code
       res <- translate(surv_reg() %>% set_engine(NULL))
-    Message
-      Used `engine = 'survival'` for translation.
+    Condition
+      Error in `set_engine()`:
+      ! Missing engine. Possible mode/engine combinations are: regression {flexsurv, survival}.
 
 # deprecation warning
 
diff --git a/tests/testthat/_snaps/svm_linear.md b/tests/testthat/_snaps/svm_linear.md
index 10f05e864..7edcaf122 100644
--- a/tests/testthat/_snaps/svm_linear.md
+++ b/tests/testthat/_snaps/svm_linear.md
@@ -20,8 +20,8 @@
     Code
       translate(svm_linear(mode = "regression") %>% set_engine(NULL))
     Condition
-      Error in `translate.default()`:
-      ! Please set an engine.
+      Error in `set_engine()`:
+      ! Missing engine. Possible mode/engine combinations are: classification {LiblineaR, kernlab} and regression {LiblineaR, kernlab}.
 
 ---
 
diff --git a/tests/testthat/_snaps/svm_poly.md b/tests/testthat/_snaps/svm_poly.md
index be1508036..b2430e8c2 100644
--- a/tests/testthat/_snaps/svm_poly.md
+++ b/tests/testthat/_snaps/svm_poly.md
@@ -28,6 +28,6 @@
     Code
       svm_poly() %>% set_engine(NULL) %>% translate()
     Condition
-      Error in `translate.default()`:
-      ! Please set an engine.
+      Error in `set_engine()`:
+      ! Missing engine. Possible mode/engine combinations are: classification {kernlab} and regression {kernlab}.
 
diff --git a/tests/testthat/_snaps/svm_rbf.md b/tests/testthat/_snaps/svm_rbf.md
index d7649eb3b..6ad5c97ac 100644
--- a/tests/testthat/_snaps/svm_rbf.md
+++ b/tests/testthat/_snaps/svm_rbf.md
@@ -48,6 +48,6 @@
     Code
       translate(svm_rbf(mode = "regression") %>% set_engine(NULL))
     Condition
-      Error in `translate.default()`:
-      ! Please set an engine.
+      Error in `set_engine()`:
+      ! Missing engine. Possible mode/engine combinations are: classification {kernlab, liquidSVM} and regression {kernlab, liquidSVM}.
 
diff --git a/tests/testthat/test-engines.R b/tests/testthat/test-engines.R
new file mode 100644
index 000000000..68b612c52
--- /dev/null
+++ b/tests/testthat/test-engines.R
@@ -0,0 +1,8 @@
+test_that("NULL engines", {
+  # See issue https://github.com/tidymodels/parsnip/issues/1242
+
+  expect_snapshot(
+    set_engine(nearest_neighbor(), NULL),
+    error = TRUE
+  )
+})
diff --git a/tests/testthat/test-mlp_keras.R b/tests/testthat/test-mlp_keras.R
index 8581a2530..2b7ba2cc3 100644
--- a/tests/testthat/test-mlp_keras.R
+++ b/tests/testthat/test-mlp_keras.R
@@ -252,6 +252,7 @@ test_that('all keras activation functions', {
   skip_on_cran()
   skip_if_not_installed("keras")
   skip_if_not_installed("modeldata")
+  skip_if_not_installed("dials", minimum_version = "1.3.0.9000")
   skip_if(!is_tf_ok())
 
   act <- parsnip:::keras_activations()
diff --git a/tests/testthat/test-rand_forest.R b/tests/testthat/test-rand_forest.R
index 242b14cba..647b06908 100644
--- a/tests/testthat/test-rand_forest.R
+++ b/tests/testthat/test-rand_forest.R
@@ -8,7 +8,10 @@ test_that('updating', {
 })
 
 test_that('bad input', {
-  expect_snapshot(res <- translate(rand_forest(mode = "classification") %>% set_engine(NULL)))
+  expect_snapshot(res <-
+                    translate(rand_forest(mode = "classification") %>%
+                                set_engine(NULL)),
+                  error = TRUE)
   expect_snapshot(error = TRUE, rand_forest(mode = "time series"))
   expect_snapshot(error = TRUE, translate(rand_forest(mode = "classification") %>% set_engine("wat?")))
 })
diff --git a/tests/testthat/test-surv_reg.R b/tests/testthat/test-surv_reg.R
index 8a0d34582..366a8e898 100644
--- a/tests/testthat/test-surv_reg.R
+++ b/tests/testthat/test-surv_reg.R
@@ -13,7 +13,7 @@ test_that('bad input', {
 
   expect_snapshot(error = TRUE, surv_reg(mode = ", classification"))
   expect_snapshot(error = TRUE, translate(surv_reg() %>% set_engine("wat")))
-  expect_snapshot(res <- translate(surv_reg() %>% set_engine(NULL)))
+  expect_snapshot(res <- translate(surv_reg() %>% set_engine(NULL)), error = TRUE)
 })
 
 test_that("deprecation warning", {