diff --git a/src/GeoTimeZone/Calculator.php b/src/GeoTimeZone/Calculator.php
index 461df03..8a069d8 100644
--- a/src/GeoTimeZone/Calculator.php
+++ b/src/GeoTimeZone/Calculator.php
@@ -18,6 +18,10 @@ class Calculator
      */
     public function __construct($dataDirectory = null)
     {
+	if (!extension_loaded("geos")) {
+            throw new ErrorException('Required dependency geos extension not installed');
+	}
+
         if (isset($dataDirectory) && is_dir($dataDirectory)) {
             $this->quadrantTree = new Tree($dataDirectory);
             $this->quadrantTree->initializeDataTree();
diff --git a/src/GeoTimeZone/UpdaterData.php b/src/GeoTimeZone/UpdaterData.php
index 61c3122..f126ca3 100755
--- a/src/GeoTimeZone/UpdaterData.php
+++ b/src/GeoTimeZone/UpdaterData.php
@@ -29,6 +29,10 @@ class UpdaterData
      */
     public function __construct($dataDirectory = null)
     {
+	if (!extension_loaded("geos")) {
+            throw new ErrorException('Required dependency geos extension not installed');
+	}
+
         if ($dataDirectory == null) {
             throw new ErrorException("ERROR: Invalid data directory.");
         }else{