diff --git a/src/Traits/ParsesCoordinates.php b/src/Traits/ParsesCoordinates.php
index 926c41b..b612246 100644
--- a/src/Traits/ParsesCoordinates.php
+++ b/src/Traits/ParsesCoordinates.php
@@ -16,7 +16,7 @@ protected function parsePointCoordinates(string $coordinates): array
         return [
             'longitude' => (float) $parts[0],
             'latitude' => (float) ($parts[1] ?? 0),
-            'altitude' => isset($parts[2]) ? (float) $parts[2] : 0,
+            'altitude' => isset($parts[2]) ? (float) $parts[2] : 0.0,
         ];
     }
 
@@ -35,7 +35,7 @@ protected function parseLineStringCoordinates(string $coordinates): array
                 $coords[] = [
                     'longitude' => (float) $parts[0],
                     'latitude' => (float) $parts[1],
-                    'altitude' => isset($parts[2]) ? (float) $parts[2] : 0,
+                    'altitude' => isset($parts[2]) ? (float) $parts[2] : 0.0,
                 ];
             }
         }
diff --git a/tests/AltitudeTest.php b/tests/AltitudeTest.php
new file mode 100644
index 0000000..250c8ef
--- /dev/null
+++ b/tests/AltitudeTest.php
@@ -0,0 +1,47 @@
+<?php
+
+use PlinCode\KmlParser\KmlParser;
+
+function kmlWithCoordinates(string $coordinates): string
+{
+    return <<<XML
+<?xml version="1.0" encoding="UTF-8"?>
+<kml xmlns="http://www.opengis.net/kml/2.2">
+    <Document>
+        <Placemark>
+            <Point>
+                <coordinates>{$coordinates}</coordinates>
+            </Point>
+        </Placemark>
+        <Placemark>
+            <LineString>
+                <coordinates>{$coordinates} 7.9,45.9</coordinates>
+            </LineString>
+        </Placemark>
+    </Document>
+</kml>
+XML;
+}
+
+it('returns a float altitude when the coordinate omits it', function () {
+    $placemarks = (new KmlParser)->loadFromString(kmlWithCoordinates('7.7,45.8'))->getPlacemarks();
+
+    expect($placemarks[0]['coordinates']['altitude'])->toBeFloat()
+        ->and($placemarks[1]['coordinates'][0]['altitude'])->toBeFloat()
+        ->and($placemarks[1]['coordinates'][1]['altitude'])->toBeFloat();
+});
+
+it('returns a float altitude when the coordinate declares it', function () {
+    $placemark = (new KmlParser)->loadFromString(kmlWithCoordinates('7.7,45.8,12'))->getPlacemarks()[0];
+
+    expect($placemark['coordinates']['altitude'])->toBeFloat()
+        ->and($placemark['coordinates']['altitude'])->toBe(12.0);
+});
+
+it('keeps the altitude a float through to GeoJSON', function () {
+    $geometry = (new KmlParser)->loadFromString(kmlWithCoordinates('7.7,45.8'))
+        ->toGeoJson()['features'][0]['geometry'];
+
+    expect($geometry['coordinates'][2])->toBeFloat()
+        ->and($geometry['coordinates'])->toBe([7.7, 45.8, 0.0]);
+});