diff --git a/R/summarize_change.R b/R/summarize_change.R
index 6cca7d36e9..e6fd1d5fd7 100644
--- a/R/summarize_change.R
+++ b/R/summarize_change.R
@@ -70,7 +70,7 @@ a_change_from_baseline <- function(df,
   custom_stat_functions <- default_and_custom_stats_list$custom_stats
 
   # Adding automatically extra parameters to the statistic function (see ?rtables::additional_fun_params)
-  extra_afun_params <- names(get_additional_analysis_fun_parameters(add_alt_df = FALSE))
+  extra_afun_params <- names(list(...)$.additional_fun_parameters)
   x_stats <- .apply_stat_functions(
     default_stat_fnc = s_change_from_baseline,
     custom_stat_fnc_list = custom_stat_functions,
@@ -82,7 +82,10 @@ a_change_from_baseline <- function(df,
   )
 
   # Fill in with formatting defaults if needed
-  .stats <- get_stats("analyze_vars_numeric", stats_in = .stats)
+  .stats <- c(
+    get_stats("analyze_vars_numeric", stats_in = .stats),
+    names(custom_stat_functions) # Additional stats from custom functions
+  )
   .formats <- get_formats_from_stats(.stats, .formats)
   .labels <- get_labels_from_stats(.stats, .labels)
   .indent_mods <- get_indents_from_stats(.stats, .indent_mods)
@@ -177,9 +180,10 @@ summarize_change <- function(lyt,
   extra_args <- c(extra_args, "variables" = list(variables), ...)
 
   # Adding all additional information from layout to analysis functions (see ?rtables::additional_fun_params)
+  extra_args[[".additional_fun_parameters"]] <- get_additional_analysis_fun_parameters(add_alt_df = FALSE)
   formals(a_change_from_baseline) <- c(
     formals(a_change_from_baseline),
-    get_additional_analysis_fun_parameters()
+    extra_args[[".additional_fun_parameters"]]
   )
 
   # Main analysis call - Nothing with .* -> these should be dedicated to the analysis function
diff --git a/R/utils_default_stats_formats_labels.R b/R/utils_default_stats_formats_labels.R
index 606571c2e1..2b47ca88c6 100644
--- a/R/utils_default_stats_formats_labels.R
+++ b/R/utils_default_stats_formats_labels.R
@@ -126,6 +126,7 @@ get_stats <- function(method_groups = "analyze_vars_numeric", stats_in = NULL, a
   out <- list(default_stats = NULL, custom_stats = NULL)
   if (is.list(stats_in)) {
     is_custom_fnc <- sapply(stats_in, is.function)
+    checkmate::assert_list(stats_in[is_custom_fnc], types = "function", names = "named")
     out[["custom_stats"]] <- stats_in[is_custom_fnc]
     out[["default_stats"]] <- unlist(stats_in[!is_custom_fnc])
   } else {
@@ -139,7 +140,7 @@ get_stats <- function(method_groups = "analyze_vars_numeric", stats_in = NULL, a
 .apply_stat_functions <- function(default_stat_fnc, custom_stat_fnc_list, args_list) {
   # Default checks
   checkmate::assert_function(default_stat_fnc)
-  checkmate::assert_list(custom_stat_fnc_list, types = "function", null.ok = TRUE)
+  checkmate::assert_list(custom_stat_fnc_list, types = "function", null.ok = TRUE, names = "named")
   checkmate::assert_list(args_list)
 
   # Checking custom stats have same formals
diff --git a/tests/testthat/_snaps/summarize_change.md b/tests/testthat/_snaps/summarize_change.md
index b0e8774d89..9752712464 100644
--- a/tests/testthat/_snaps/summarize_change.md
+++ b/tests/testthat/_snaps/summarize_change.md
@@ -499,3 +499,20 @@
         Median          -2.00    
         Min - Max   -2.00 - -2.00
 
+# summarize_change works with custom statistical functions
+
+    Code
+      res
+    Output
+                  all obs
+      ———————————————————
+      V1                 
+        n            3   
+        my_stat    1.00  
+      V2                 
+        n            3   
+        my_stat    0.83  
+      V3                 
+        n            3   
+        my_stat    0.67  
+
diff --git a/tests/testthat/test-summarize_change.R b/tests/testthat/test-summarize_change.R
index 2b3b457a81..adf60ffc68 100644
--- a/tests/testthat/test-summarize_change.R
+++ b/tests/testthat/test-summarize_change.R
@@ -123,7 +123,15 @@ testthat::test_that("summarize_change works with custom statistical functions",
     summarize_change(
       "CHG",
       variables = list(value = "AVAL", baseline_flag = "ABLFLL"),
-      .stats = c("n", "my_stat" = function(df, ...) mean(df$AVISIT, na.rm = TRUE))
+      .stats = c("n", "my_stat" = function(df, ...) {
+        a <- mean(df$AVAL, na.rm = TRUE)
+        b <- list(...)$.N_row
+        a / b
+      }),
+      .formats = c("my_stat" = function(x, ...) sprintf("%.2f", x))
     ) %>%
     build_table(dta_test)
+
+  res <- testthat::expect_silent(result)
+  testthat::expect_snapshot(res)
 })
diff --git a/vignettes/tern_functions_guide.Rmd b/vignettes/tern_functions_guide.Rmd
index 200d1764fc..929c106ff2 100644
--- a/vignettes/tern_functions_guide.Rmd
+++ b/vignettes/tern_functions_guide.Rmd
@@ -115,17 +115,21 @@ fix_layout %>%
   print()
 ```
 
-Adding a custom statistic:
+Adding a custom statistic (and custom format):
 ```{r}
 # changing n count format and label and indentation
 fix_layout %>%
-  summarize_change("CHG",
-    variables = list(value = "AVAL", baseline_flag = "ABLFLL"),
-    .stats = c("n", "mean", "arg" = function(x, ...) mean(x)),
-    .formats = c(n = function(x, ...) as.character(x * 100))
-  ) %>% # Note you need ...!!!
-  build_table(dta_test) %>%
-  print()
+    summarize_change(
+      "CHG",
+      variables = list(value = "AVAL", baseline_flag = "ABLFLL"),
+      .stats = c("n", "my_stat" = function(df, ...) {
+        a <- mean(df$AVAL, na.rm = TRUE)
+        b <- list(...)$.N_row # It has access at all `?rtables::additional_fun_params`
+        a / b
+      }),
+      .formats = c("my_stat" = function(x, ...) sprintf("%.2f", x))
+    ) %>%
+    build_table(dta_test)
 ```