diff --git a/Zend/tests/custom_assert_deprecation.phpt b/Zend/tests/custom_assert_forbidden.phpt
similarity index 53%
rename from Zend/tests/custom_assert_deprecation.phpt
rename to Zend/tests/custom_assert_forbidden.phpt
index b4e22843ddb..492a656f394 100644
--- a/Zend/tests/custom_assert_deprecation.phpt
+++ b/Zend/tests/custom_assert_forbidden.phpt
@@ -9,4 +9,4 @@ function assert() {}
 
 ?>
 --EXPECTF--
-Deprecated: Defining a custom assert() function is deprecated, as the function has special semantics in %s on line %d
+Fatal error: Defining a custom assert() function is not allowed, as the function has special semantics in %s on line %d
diff --git a/Zend/zend_compile.c b/Zend/zend_compile.c
index e6b6d9fc09e..cfe03e71f94 100644
--- a/Zend/zend_compile.c
+++ b/Zend/zend_compile.c
@@ -5740,8 +5740,8 @@ static void zend_begin_func_decl(znode *result, zend_op_array *op_array, zend_as
 	}
 
 	if (zend_string_equals_literal_ci(unqualified_name, "assert")) {
-		zend_error(E_DEPRECATED,
-			"Defining a custom assert() function is deprecated, "
+		zend_error(E_COMPILE_ERROR,
+			"Defining a custom assert() function is not allowed, "
 			"as the function has special semantics");
 	}