diff --git a/src/SmartIpLocation.php b/src/SmartIpLocation.php
--- a/src/SmartIpLocation.php
+++ b/src/SmartIpLocation.php
@@ -200,6 +200,17 @@
    * {@inh  eritdoc}
    */
   public function set(string $key, mixed $value): SmartIpLocationInterface|static {
+    // Country DB lookups may return empty strings or numeric strings for
+    // lat/lon. Normalize before assigning to typed float properties.
+    if (in_array($key, ['latitude', 'longitude'], TRUE)) {
+      if ($value === '' || $value === NULL) {
+        return $this;
+      }
+      if (is_string($value) || is_numeric($value)) {
+        $value = (float) $value;
+      }
+    }
+
     if (isset($this->{$key})) {
       $this->{$key} = $value;
       $this->allData[$key] = $value;