diff --git a/Tests/MappedRow/MappedRowTest.php b/Tests/MappedRow/MappedRowTest.php
index 21a572f..3844c54 100644
--- a/Tests/MappedRow/MappedRowTest.php
+++ b/Tests/MappedRow/MappedRowTest.php
@@ -23,7 +23,10 @@ public function testinvalidKey($key, $cols, $row)
 
     public function invalidKeyDataProvider()
     {
-        $cols = ['a', 'c'];
+        $cols = [
+            'a' => 0,
+            'c' => 1,
+        ];
         $mockRow = $this->createMock(Row::class);
         $mockRow
             ->method('getCellIterator')
@@ -31,8 +34,16 @@ public function invalidKeyDataProvider()
         ;
         yield ['invalidCellKey', $cols, $mockRow];
 
-        $cols = [455, 377];
-        yield ['invalidCellKey', $cols, $mockRow];
+        $numericCols = [
+            455 => 1,
+            377 => 0,
+        ];
+        $numericMockRow = $this->createMock(Row::class);
+        $numericMockRow
+            ->method('getCellIterator')
+            ->willReturn(new \ArrayIterator([$this->generateMockCell(4), $this->generateMockCell(5)]))
+        ;
+        yield ['invalidCellKey', $numericCols, $numericMockRow];
     }
 
     /**
diff --git a/Tests/SpreadSheetMappingTest.php b/Tests/SpreadSheetMappingTest.php
index 70511d2..6430fe9 100644
--- a/Tests/SpreadSheetMappingTest.php
+++ b/Tests/SpreadSheetMappingTest.php
@@ -11,9 +11,13 @@
 class SpreadSheetMappingTest extends TestCase
 {
 
-    public function testBasicIntegration()
+    /**
+     * @param string $filename
+     * @dataProvider basicIntegrationFilenameProvider
+     */
+    public function testBasicIntegration($filename)
     {
-        $workbook = IOFactory::load('Tests/testData/simpleok.xlsx');
+        $workbook = IOFactory::load($filename);
         $worksheet = $workbook->getSheet(0);
 
         $mapping = new Mapping();
@@ -31,6 +35,15 @@ public function testBasicIntegration()
         }
     }
 
+    /**
+     * @return \Generator|string[]
+     */
+    public function basicIntegrationFilenameProvider()
+    {
+        yield ['Tests/testData/simpleok.xlsx'];
+        yield ['Tests/testData/gaps.xlsx'];
+    }
+
     public function testOnlyColumns()
     {
         $workbook = IOFactory::load('Tests/testData/simpleok.xlsx');
diff --git a/Tests/testData/gaps.xlsx b/Tests/testData/gaps.xlsx
new file mode 100644
index 0000000..bae2295
Binary files /dev/null and b/Tests/testData/gaps.xlsx differ
diff --git a/src/MappedRow/MappedRow.php b/src/MappedRow/MappedRow.php
index d17ef92..63c79df 100644
--- a/src/MappedRow/MappedRow.php
+++ b/src/MappedRow/MappedRow.php
@@ -2,8 +2,6 @@
 
 namespace Dpiquet\SpreadsheetMapping\MappedRow;
 
-
-use Dpiquet\Mapping\Mapping;
 use Dpiquet\SpreadsheetMapping\MappedRow\Exception\InvalidKeyException;
 use Dpiquet\SpreadsheetMapping\MappedRow\Exception\MissingValueException;
 use PhpOffice\PhpSpreadsheet\Worksheet\Row;
@@ -47,7 +45,7 @@ public function __construct(array $map, Row $row)
      * @throws MissingValueException
      */
     public function get($key) {
-        if (!in_array($key, $this->map)) {
+        if (!array_key_exists($key, $this->map)) {
             throw new InvalidKeyException($key);
         }