diff --git a/DESCRIPTION b/DESCRIPTION
index ca8c36a2..6420507e 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -1,7 +1,7 @@
 Package: report
 Type: Package
 Title: Automated Reporting of Results and Statistical Models
-Version: 0.6.3.1
+Version: 0.6.3.2
 Authors@R:
     c(person(given = "Dominique",
              family = "Makowski",
diff --git a/NEWS.md b/NEWS.md
index 5a417704..1bdadae8 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -2,6 +2,7 @@
 
 Bug fixes
 
+* Fixed custom effect size rules not being correctly reported as custom rules (#458)
 * Fix `report()` crash when character vector has only one unique value (#578).
 
 # report 0.6.3
diff --git a/R/report_effectsize.R b/R/report_effectsize.R
index c17c9154..674b2f20 100644
--- a/R/report_effectsize.R
+++ b/R/report_effectsize.R
@@ -102,11 +102,17 @@ print.report_effectsize <- function(x, ...) {
       field2013 = "Field's (2013)",
       landis1977 = "Landis' (1977)"
     )
-    effect_text <- paste0(
-      "Effect sizes were labelled following ",
-      effsize_name,
-      " recommendations."
-    )
+    if (is.null(effsize_name)) {
+      effect_text <- paste0(
+        "Effect sizes were labelled following a custom set of rules."
+      )
+    } else {
+      effect_text <- paste0(
+        "Effect sizes were labelled following ",
+        effsize_name,
+        " recommendations."
+      )
+    }
   } else {
     effect_text <- paste0(
       "Effect sizes were labelled following a custom set of rules."
diff --git a/tests/testthat/test-report.htest-t-test.R b/tests/testthat/test-report.htest-t-test.R
index 1ffb3e2d..0612b503 100644
--- a/tests/testthat/test-report.htest-t-test.R
+++ b/tests/testthat/test-report.htest-t-test.R
@@ -160,4 +160,15 @@ test_that("report.htest-t-test", {
     variant = "windows",
     report_effectsize(x, rules = "gignac2016", type = "g")
   )
+  
+  # custom rules ---------------------
+  custom_rules <- effectsize::rules(1, c("tiny", "yeah okay"), name = "Unknown")
+  expect_snapshot(
+    variant = "windows",
+    report_effectsize(x, rules = custom_rules)
+  )
+  expect_snapshot(
+    variant = "windows",
+    report(x, rules = custom_rules)
+  )
 })
diff --git a/tests/testthat/test-text_effectsize.R b/tests/testthat/test-text_effectsize.R
new file mode 100644
index 00000000..21716c58
--- /dev/null
+++ b/tests/testthat/test-text_effectsize.R
@@ -0,0 +1,66 @@
+test_that(".text_effectsize handles custom rules correctly", {
+  # Test NULL input
+  expect_equal(report:::.text_effectsize(NULL), "")
+  
+  # Test known predefined rules
+  expect_equal(
+    report:::.text_effectsize("cohen1988"),
+    "Effect sizes were labelled following Cohen's (1988) recommendations."
+  )
+  expect_equal(
+    report:::.text_effectsize("sawilowsky2009"),
+    "Effect sizes were labelled following Savilowsky's (2009) recommendations."
+  )
+  expect_equal(
+    report:::.text_effectsize("gignac2016"),
+    "Effect sizes were labelled following Gignac's (2016) recommendations."
+  )
+  expect_equal(
+    report:::.text_effectsize("funder2019"),
+    "Effect sizes were labelled following Funder's (2019) recommendations."
+  )
+  expect_equal(
+    report:::.text_effectsize("lovakov2021"),
+    "Effect sizes were labelled following Lovakov's (2021) recommendations."
+  )
+  expect_equal(
+    report:::.text_effectsize("evans1996"),
+    "Effect sizes were labelled following Evans's (1996) recommendations."
+  )
+  expect_equal(
+    report:::.text_effectsize("chen2010"),
+    "Effect sizes were labelled following Chen's (2010) recommendations."
+  )
+  expect_equal(
+    report:::.text_effectsize("field2013"),
+    "Effect sizes were labelled following Field's (2013) recommendations."
+  )
+  expect_equal(
+    report:::.text_effectsize("landis1977"),
+    "Effect sizes were labelled following Landis' (1977) recommendations."
+  )
+  
+  # Test custom rule names (strings not in predefined list)
+  expect_equal(
+    report:::.text_effectsize("Unknown"),
+    "Effect sizes were labelled following a custom set of rules."
+  )
+  expect_equal(
+    report:::.text_effectsize("MyCustomRules"),
+    "Effect sizes were labelled following a custom set of rules."
+  )
+  expect_equal(
+    report:::.text_effectsize("CustomRule2024"),
+    "Effect sizes were labelled following a custom set of rules."
+  )
+  
+  # Test non-character input (should also return custom rules text)
+  expect_equal(
+    report:::.text_effectsize(123),
+    "Effect sizes were labelled following a custom set of rules."
+  )
+  expect_equal(
+    report:::.text_effectsize(list()),
+    "Effect sizes were labelled following a custom set of rules."
+  )
+})
\ No newline at end of file