diff --git a/src/CNPJ.php b/src/CNPJ.php
index f80431c..dbfe27d 100644
--- a/src/CNPJ.php
+++ b/src/CNPJ.php
@@ -41,7 +41,7 @@ public function isValid()
 
         // Validate first check digit
         for ($i = 0, $j = 5, $sum = 0; $i < 12; $i++) {
-            $sum += $this->value{$i} * $j;
+            $sum += $this->value[$i] * $j;
             $j = ($j == 2) ? 9 : $j - 1;
         }
         $result = $sum % 11;
@@ -53,13 +53,13 @@ public function isValid()
 
         // Validate second check digit
         for ($i = 0, $j = 6, $sum = 0; $i < 13; $i++) {
-            $sum += $this->value{$i} * $j;
+            $sum += $this->value[$i] * $j;
             $j = ($j == 2) ? 9 : $j - 1;
         }
         $result = $sum % 11;
         
 
-        return $this->value{13} == ($result < 2 ? 0 : 11 - $result);
+        return $this->value[13] == ($result < 2 ? 0 : 11 - $result);
     }
 
     /**
diff --git a/src/CPF.php b/src/CPF.php
index 419e945..86a6368 100644
--- a/src/CPF.php
+++ b/src/CPF.php
@@ -39,20 +39,20 @@ public function isValid()
 
         // Validate first check digit
         for ($i = 0, $j = 10, $sum = 0; $i < 9; $i++, $j--)
-            $sum += $this->value{$i} * $j;
+            $sum += $this->value[$i] * $j;
 
         $result = $sum % 11;
 
-        if ($this->value{9} != ($result < 2 ? 0 : 11 - $result))
+        if ($this->value[9] != ($result < 2 ? 0 : 11 - $result))
             return false;
 
         // Validate first second digit
         for ($i = 0, $j = 11, $sum = 0; $i < 10; $i++, $j--)
-            $sum += $this->value{$i} * $j;
+            $sum += $this->value[$i] * $j;
 
         $result = $sum % 11;
 
-        return $this->value{10} == ($result < 2 ? 0 : 11 - $result);
+        return $this->value[10] == ($result < 2 ? 0 : 11 - $result);
     }
 
     /**