diff --git a/src/ol/format/GPX.js b/src/ol/format/GPX.js
index b4b0bbfa91..e9e23de5f6 100644
--- a/src/ol/format/GPX.js
+++ b/src/ol/format/GPX.js
@@ -66,7 +66,7 @@ inherits(GPX, XMLFeature);
 
 /**
  * @const
- * @type {Array.<string>}
+ * @type {Array.<null|string>}
  */
 const NAMESPACE_URIS = [
   null,
diff --git a/src/ol/format/KML.js b/src/ol/format/KML.js
index e67212c356..edfdd1dbf3 100644
--- a/src/ol/format/KML.js
+++ b/src/ol/format/KML.js
@@ -324,7 +324,7 @@ const GX_NAMESPACE_URIS = [
 
 /**
  * @const
- * @type {Array.<string>}
+ * @type {Array.<null|string>}
  */
 const NAMESPACE_URIS = [
   null,
diff --git a/src/ol/format/OSMXML.js b/src/ol/format/OSMXML.js
index 29e3959ae4..c0b8ad611e 100644
--- a/src/ol/format/OSMXML.js
+++ b/src/ol/format/OSMXML.js
@@ -38,7 +38,7 @@ inherits(OSMXML, XMLFeature);
 
 /**
  * @const
- * @type {Array.<string>}
+ * @type {Array.<null>}
  */
 const NAMESPACE_URIS = [null];
 
diff --git a/src/ol/format/OWS.js b/src/ol/format/OWS.js
index e00c983bda..66c3f76b4b 100644
--- a/src/ol/format/OWS.js
+++ b/src/ol/format/OWS.js
@@ -20,7 +20,7 @@ inherits(OWS, XML);
 
 /**
  * @const
- * @type {Array.<string>}
+ * @type {Array.<null|string>}
  */
 const NAMESPACE_URIS = [null, 'http://www.opengis.net/ows/1.1'];
 
diff --git a/src/ol/format/WMSCapabilities.js b/src/ol/format/WMSCapabilities.js
index 73f3c3cf34..d24dcaa786 100644
--- a/src/ol/format/WMSCapabilities.js
+++ b/src/ol/format/WMSCapabilities.js
@@ -32,7 +32,7 @@ inherits(WMSCapabilities, XML);
 
 /**
  * @const
- * @type {Array.<string>}
+ * @type {Array.<null|string>}
  */
 const NAMESPACE_URIS = [
   null,
diff --git a/src/ol/format/WMTSCapabilities.js b/src/ol/format/WMTSCapabilities.js
index 9806dec327..281ddc1301 100644
--- a/src/ol/format/WMTSCapabilities.js
+++ b/src/ol/format/WMTSCapabilities.js
@@ -33,7 +33,7 @@ inherits(WMTSCapabilities, XML);
 
 /**
  * @const
- * @type {Array.<string>}
+ * @type {Array.<null|string>}
  */
 const NAMESPACE_URIS = [
   null,
@@ -43,7 +43,7 @@ const NAMESPACE_URIS = [
 
 /**
  * @const
- * @type {Array.<string>}
+ * @type {Array.<null|string>}
  */
 const OWS_NAMESPACE_URIS = [
   null,