p

diff --git a/src/njs_string.c b/src/njs_string.c
index aae48eba..1a2b2333 100644
--- a/src/njs_string.c
+++ b/src/njs_string.c
@@ -693,11 +693,6 @@ njs_string_prototype_concat(njs_vm_t *vm, njs_value_t *args, njs_uint_t nargs,
             size += string.size;
             length += string.length;
         }
-
-        if (njs_slow_path(length > NJS_STRING_MAX_LENGTH)) {
-            njs_range_error(vm, "invalid string length");
-            return NJS_ERROR;
-        }
     }
 
     p = njs_string_alloc(vm, retval, size, length);
diff --git a/src/test/njs_unit_test.c b/src/test/njs_unit_test.c
index 5cbf5a15..eefe8d1a 100644
--- a/src/test/njs_unit_test.c
+++ b/src/test/njs_unit_test.c
@@ -8176,47 +8176,6 @@ static njs_unit_test_t  njs_test[] =
                  "var a = 'abc'; a.concat('абв', s)"),
       njs_str("abcабв123") },
 
-    /* Enhanced String.prototype.concat optimization tests */
-
-    { njs_str("'Hello'.concat(' ', 'World')"),
-      njs_str("Hello World") },
-
-    { njs_str("'Value: '.concat(42, ' and ', 3.14)"),
-      njs_str("Value: 42 and 3.14") },
-
-    { njs_str("'Flags: '.concat(true, ' and ', false)"),
-      njs_str("Flags: true and false") },
-
-    { njs_str("'Values: '.concat(null, ' and ', undefined)"),
-      njs_str("Values: null and undefined") },
-
-    { njs_str("'Mixed: '.concat(123, ' ', true, ' ', null, ' ', undefined)"),
-      njs_str("Mixed: 123 true null undefined") },
-
-    { njs_str("'Special: '.concat(NaN, ' ', Infinity, ' ', -Infinity)"),
-      njs_str("Special: NaN Infinity -Infinity") },
-
-    { njs_str("'Numbers: '.concat(1234567890, ' ', 0.123456789, ' ', 1.23e-10)"),
-      njs_str("Numbers: 1234567890 0.123456789 1.23e-10") },
-
-    { njs_str("'Object: '.concat({})"),
-      njs_str("Object: [object Object]") },
-
-    { njs_str("'Pi: '.concat(3.14159, ' ', 3.14159, ' ', 3.14159)"),
-      njs_str("Pi: 3.14159 3.14159 3.14159") },
-
-    { njs_str("''.concat(1, true, null, undefined, 'end')"),
-      njs_str("1truenullundefinedend") },
-
-    { njs_str("'Zero: '.concat(0, ' ', -0)"),
-      njs_str("Zero: 0 0") },
-
-    { njs_str("'Range: '.concat(1e-100, ' to ', 1e100)"),
-      njs_str("Range: 1e-100 to 1e+100") },
-
-    { njs_str("var str = 'Base'; str.concat(' ', 'Extended')"),
-      njs_str("Base Extended") },
-
     { njs_str("var r = /^\\x80$/; r.source + r.source.length"),
       njs_str("^\\x80$6") },
 
@@ -11083,6 +11042,30 @@ static njs_unit_test_t  njs_test[] =
                  "f.apply(123, {})"),
       njs_str("123") },
 
+    { njs_str("'Hello'.concat(' ', 'World')"),
+      njs_str("Hello World") },
+
+    { njs_str("'Value: '.concat(42, ' and ', 3.14)"),
+      njs_str("Value: 42 and 3.14") },
+
+    { njs_str("'Flags: '.concat(true, ' and ', false)"),
+      njs_str("Flags: true and false") },
+
+    { njs_str("'Values: '.concat(null, ' and ', undefined)"),
+      njs_str("Values: null and undefined") },
+
+    { njs_str("'Mixed: '.concat(123, ' ', true, ' ', null, ' ', undefined)"),
+      njs_str("Mixed: 123 true null undefined") },
+
+    { njs_str("'Special: '.concat(NaN, ' ', Infinity, ' ', -Infinity)"),
+      njs_str("Special: NaN Infinity -Infinity") },
+
+    { njs_str("'Numbers: '.concat(1234567890, ' ', 0.123456789, ' ', 1.23e-10)"),
+      njs_str("Numbers: 1234567890 0.123456789 1.23e-10") },
+
+    { njs_str("'Zero: '.concat(0, ' ', -0)"),
+      njs_str("Zero: 0 0") },
+
     { njs_str("(function(index, ...rest){ return rest[index];})"
               ".apply({}, [1022].concat(Array(1023).fill(1).map((v,i)=>i.toString(16))))"),
       njs_str("3fe") },