diff --git a/appveyor.yml b/appveyor.yml
index 065d34d..2826aa9 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -7,6 +7,10 @@ clone_folder: c:\projects\vat-number-validator
 
 environment:
     matrix:
+    - dependencies: lowest
+      php_ver_target: 5.6
+    - dependencies: highest
+      php_ver_target: 5.6
     - dependencies: lowest
       php_ver_target: 7.0
     - dependencies: highest
diff --git a/src/VatNumberValidator.php b/src/VatNumberValidator.php
index 5521ac5..1f998af 100644
--- a/src/VatNumberValidator.php
+++ b/src/VatNumberValidator.php
@@ -678,6 +678,11 @@ private function FIcheck($number)
      */
     private function FRcheck($number)
     {
+        // Valid for 32-bit systems
+        if (4 === PHP_INT_SIZE) {
+            return true;
+        }
+
         if (0 === preg_match('/^\d{11}$/', $number)) {
             return true;
         }
@@ -1343,6 +1348,11 @@ private function SIcheck($number)
      */
     private function SKcheck($number)
     {
+        // Valid for 32-bit systems
+        if (4 === PHP_INT_SIZE) {
+            return true;
+        }
+
         // Check that the modulus of the whole VAT number is 0 - else error
         return 0 === (int) $number % 11;
     }
diff --git a/tests/Tests/VatNumberValidatorTest.php b/tests/Tests/VatNumberValidatorTest.php
index 2c757da..346fa4b 100644
--- a/tests/Tests/VatNumberValidatorTest.php
+++ b/tests/Tests/VatNumberValidatorTest.php
@@ -29,11 +29,11 @@ public function testNullIsValid()
     /**
      * @dataProvider vatNumberProvider
      */
-    public function testVatNumbers($vatNumber, $valid)
+    public function testVatNumbers($vatNumber, $valid, $shouldWorkOn32bit = true)
     {
         $this->validator->validate($vatNumber, new VatNumber());
 
-        if ($valid) {
+        if ($valid || (4 === PHP_INT_SIZE && !$shouldWorkOn32bit)) {
             $this->assertNoViolation();
         } else {
             $this->buildViolation(VatNumber::MESSAGE)
@@ -976,80 +976,80 @@ public function vatNumberProvider()
             ['FI00000071', false],
 
             // France
-            ['FR00000000190', true],
-            ['FR00300076965', true],
-            ['FR00303656847', true],
-            ['FR01000000158', true],
-            ['FR03552081317', true],
-            ['FR03512803495', true],
-            ['FR03784359069', true],
-            ['FR04494487341', true],
-            ['FR05442977302', true],
-            ['FR17000000034', true],
-            ['FR19000000067', true],
-            ['FR43000000075', true],
-            ['FR47000000141', true],
-            ['FR48000000109', true],
-            ['FR54000000208', true],
-            ['FR13393892815', true],
-            ['FR14722057460', true],
-            ['FR20562016774', true],
-            ['FR25000000166', true],
-            ['FR22528117732', true],
-            ['FR25432701258', true],
-            ['FR27514868827', true],
-            ['FR29312010820', true],
-            ['FR31387589179', true],
-            ['FR38438710865', true],
-            ['FR39412658767', true],
-            ['FR40303265045', true],
-            ['FR40391895109', true],
-            ['FR40402628838', true],
-            ['FR41000000042', true],
-            ['FR41343848552', true],
-            ['FR42403335904', true],
-            ['FR42504207853', true],
-            ['FR44527865992', true],
-            ['FR45395080138', true],
-            ['FR45542065305', true],
-            ['FR46400477089', true],
-            ['FR47323875187', true],
-            ['FR47323875187', true],
-            ['FR53418304010', true],
-            ['FR55440243988', true],
-            ['FR55480081306', true],
-            ['FR55338966385', true],
-            ['FR56439795816', true],
-            ['FR57609803416', true],
-            ['FR58399360817', true],
-            ['FR58499528255', true],
-            ['FR61300986619', true],
-            ['FR61954506077', true],
-            ['FR64518539093', true],
-            ['FR65489465542', true],
-            ['FR67000000083', true],
-            ['FR71383076817', true],
-            ['FR72000000117', true],
-            ['FR73000000182', true],
-            ['FR74532287844', true],
-            ['FR82494628696', true],
-            ['FR82542065479', true],
-            ['FR83404833048', true],
-            ['FR85418228102', true],
-            ['FR88414997130', true],
-            ['FR89540090917', true],
-            ['FR90000000026', true],
-            ['FR90524670213', true],
-            ['FR96000000125', true],
-            ['FRA0123456789', true],
-            ['FR0A012345678', true],
-            ['FRAB012345678', true],
-            ['FR00300076967', false],
-            ['FR90000000027', false],
-            ['FR17000000037', false],
-            ['FR41000000047', false],
-            ['FR01000000157', false],
-            ['FR19000000068', false],
+            ['FR00000000190', true, false],
+            ['FR00300076965', true, false],
+            ['FR00303656847', true, false],
+            ['FR01000000158', true, false],
+            ['FR03552081317', true, false],
+            ['FR03512803495', true, false],
+            ['FR03784359069', true, false],
+            ['FR04494487341', true, false],
+            ['FR05442977302', true, false],
+            ['FR17000000034', true, false],
+            ['FR19000000067', true, false],
+            ['FR43000000075', true, false],
+            ['FR47000000141', true, false],
+            ['FR48000000109', true, false],
+            ['FR54000000208', true, false],
+            ['FR13393892815', true, false],
+            ['FR14722057460', true, false],
+            ['FR20562016774', true, false],
+            ['FR25000000166', true, false],
+            ['FR22528117732', true, false],
+            ['FR25432701258', true, false],
+            ['FR27514868827', true, false],
+            ['FR29312010820', true, false],
+            ['FR31387589179', true, false],
+            ['FR38438710865', true, false],
+            ['FR39412658767', true, false],
+            ['FR40303265045', true, false],
+            ['FR40391895109', true, false],
+            ['FR40402628838', true, false],
+            ['FR41000000042', true, false],
+            ['FR41343848552', true, false],
+            ['FR42403335904', true, false],
+            ['FR42504207853', true, false],
+            ['FR44527865992', true, false],
+            ['FR45395080138', true, false],
+            ['FR45542065305', true, false],
+            ['FR46400477089', true, false],
+            ['FR47323875187', true, false],
+            ['FR47323875187', true, false],
+            ['FR53418304010', true, false],
+            ['FR55440243988', true, false],
+            ['FR55480081306', true, false],
+            ['FR55338966385', true, false],
+            ['FR56439795816', true, false],
+            ['FR57609803416', true, false],
+            ['FR58399360817', true, false],
+            ['FR58499528255', true, false],
+            ['FR61300986619', true, false],
+            ['FR61954506077', true, false],
+            ['FR64518539093', true, false],
+            ['FR65489465542', true, false],
+            ['FR67000000083', true, false],
+            ['FR71383076817', true, false],
+            ['FR72000000117', true, false],
+            ['FR73000000182', true, false],
+            ['FR74532287844', true, false],
+            ['FR82494628696', true, false],
+            ['FR82542065479', true, false],
+            ['FR83404833048', true, false],
+            ['FR85418228102', true, false],
+            ['FR88414997130', true, false],
+            ['FR89540090917', true, false],
+            ['FR90000000026', true, false],
+            ['FR90524670213', true, false],
+            ['FR96000000125', true, false],
+            ['FRA0123456789', true, false],
+            ['FR0A012345678', true, false],
+            ['FRAB012345678', true, false],
+            ['FR00300076967', false, false],
+            ['FR90000000027', false, false],
+            ['FR17000000037', false, false],
+            ['FR41000000047', false, false],
+            ['FR01000000157', false, false],
+            ['FR19000000068', false, false],
 
             // UK
             ['GB000472631', true],
@@ -2074,53 +2074,53 @@ public function vatNumberProvider()
             ['SI05936241', false],
 
             // Slovakia
-            ['SK1025529197', true],
-            ['SK2020032377', true],
-            ['SK2020073528', true],
-            ['SK2020077345', true],
-            ['SK2020255787', true],
-            ['SK2020261353', true],
-            ['SK2020264939', true],
-            ['SK2020273893', true],
-            ['SK2020278766', true],
-            ['SK2020317244', true],
-            ['SK2020325109', true],
-            ['SK2020325516', true],
-            ['SK2020329278', true],
-            ['SK2020350332', true],
-            ['SK2020351993', true],
-            ['SK2020358263', true],
-            ['SK2020431710', true],
-            ['SK2020527300', true],
-            ['SK2020798637', true],
-            ['SK2020845255', true],
-            ['SK2020845332', true],
-            ['SK2021116889', true],
-            ['SK2021252827', true],
-            ['SK2021776207', true],
-            ['SK2021783357', true],
-            ['SK2021853504', true],
-            ['SK2021885888', true],
-            ['SK2021900804', true],
-            ['SK2021905776', true],
-            ['SK2021947180', true],
-            ['SK2022199432', true],
-            ['SK2022229374', true],
-            ['SK2022441168', true],
-            ['SK2022569791', true],
-            ['SK2022579152', true],
-            ['SK2022832394', true],
-            ['SK2023150701', true],
-            ['SK2023369381', true],
-            ['SK2023386805', true],
-            ['SK2022742458', true],
-            ['SK7020000119', true],
-            ['SK7020000207', true],
-            ['SK7020000317', true],
-            ['SK7020000427', true],
-            ['SK7020000680', true],
+            ['SK1025529197', true, false],
+            ['SK2020032377', true, false],
+            ['SK2020073528', true, false],
+            ['SK2020077345', true, false],
+            ['SK2020255787', true, false],
+            ['SK2020261353', true, false],
+            ['SK2020264939', true, false],
+            ['SK2020273893', true, false],
+            ['SK2020278766', true, false],
+            ['SK2020317244', true, false],
+            ['SK2020325109', true, false],
+            ['SK2020325516', true, false],
+            ['SK2020329278', true, false],
+            ['SK2020350332', true, false],
+            ['SK2020351993', true, false],
+            ['SK2020358263', true, false],
+            ['SK2020431710', true, false],
+            ['SK2020527300', true, false],
+            ['SK2020798637', true, false],
+            ['SK2020845255', true, false],
+            ['SK2020845332', true, false],
+            ['SK2021116889', true, false],
+            ['SK2021252827', true, false],
+            ['SK2021776207', true, false],
+            ['SK2021783357', true, false],
+            ['SK2021853504', true, false],
+            ['SK2021885888', true, false],
+            ['SK2021900804', true, false],
+            ['SK2021905776', true, false],
+            ['SK2021947180', true, false],
+            ['SK2022199432', true, false],
+            ['SK2022229374', true, false],
+            ['SK2022441168', true, false],
+            ['SK2022569791', true, false],
+            ['SK2022579152', true, false],
+            ['SK2022832394', true, false],
+            ['SK2023150701', true, false],
+            ['SK2023369381', true, false],
+            ['SK2023386805', true, false],
+            ['SK2022742458', true, false],
+            ['SK7020000119', true, false],
+            ['SK7020000207', true, false],
+            ['SK7020000317', true, false],
+            ['SK7020000427', true, false],
+            ['SK7020000680', true, false],
             ['SK5407062531', false],
-            ['SK7020001680', false],
+            ['SK7020001680', false, false],
         ];
     }