diff --git a/R/count_bindings.R b/R/count_bindings.R
index 5601cd90..291779e3 100644
--- a/R/count_bindings.R
+++ b/R/count_bindings.R
@@ -576,6 +576,10 @@ set_outer_sort_position <- function(e, outer_sort_position) {
 set_denom_where <- function(e, denom_where) {
   denom_where <- enquo(denom_where)
 
+  if (!(inherits(e, 'tplyr_layer') | inherits(e, 'tplyr_table'))) {
+    stop('Object type should be either "tplyr_layer" or "tplyr_table"', call.=FALSE)
+  }
+
   assert_that(is_logical_or_call(denom_where),
               msg = "The `where` parameter must contain subsetting logic (enter without quotes)")
 
diff --git a/tests/testthat/test-count.R b/tests/testthat/test-count.R
index c61f0d29..3a248a2e 100644
--- a/tests/testthat/test-count.R
+++ b/tests/testthat/test-count.R
@@ -440,6 +440,17 @@ test_that("set_denom_where works as expected", {
   expect_snapshot_output(dput(t13))
 })
 
+test_that("set_denom_where errors for incompatible object type", {
+  t1 <- tplyr_table(mtcars, gear)
+
+  # Modify the object type to make it incompatible
+  class(t1) <- "environment"
+
+  # Function errors
+  t1 <- set_denom_where(t1, mpg != 21) %>%
+    expect_error("Object type should be")
+})
+
 test_that("missing counts can be set without a format and it inherits the layer format", {
   t1 <- tplyr_table(mtcars, gear) %>%
     add_layer(