diff --git a/src/GpsPoint.php b/src/GpsPoint.php
index 3078b68c..dd3fcb5b 100644
--- a/src/GpsPoint.php
+++ b/src/GpsPoint.php
@@ -53,7 +53,7 @@ private function isValidCoordinate(string $value, float $maxBoundary): bool
             $value = $this->removeDegreeSign($value);
         }
 
-        if ($value === false || $value === null) {
+        if ($value === false || $value === null || !is_numeric($value)) {
             $this->error(self::CONVERT_ERROR);
             return false;
         }
diff --git a/test/GPSPointTest.php b/test/GPSPointTest.php
index efbd47fe..83284c2a 100644
--- a/test/GPSPointTest.php
+++ b/test/GPSPointTest.php
@@ -85,10 +85,11 @@ public function basicDataProvider(): array
     public function errorMessageTestValues(): array
     {
         return [
-            ['63 47 24.691 N, 18 2 54.363 W', GpsPoint::OUT_OF_BOUNDS, '63 47 24.691 N'],
+            ['63 47 24.691 N, 18 2 54.363 W', GpsPoint::CONVERT_ERROR, '63 47 24.691 N'],
+            ['65° 4\' N,-22.728867530822754', GpsPoint::CONVERT_ERROR, '65° 4\' N'],
             ['° \' " N,° \' " E', GpsPoint::CONVERT_ERROR, '° \' " N'],
             ['° \' " N', GpsPoint::INCOMPLETE_COORDINATE, '° \' " N'],
-            ['foo,bar', GpsPoint::CONVERT_ERROR, '° \' " N'],
+            ['foo,bar', GpsPoint::CONVERT_ERROR, 'foo'],
         ];
     }
 }