diff --git a/azure-storage-blob/src/Blob/BlobRestProxy.php b/azure-storage-blob/src/Blob/BlobRestProxy.php
index ca7a6c59..9994b98a 100644
--- a/azure-storage-blob/src/Blob/BlobRestProxy.php
+++ b/azure-storage-blob/src/Blob/BlobRestProxy.php
@@ -1521,11 +1521,13 @@ public function listBlobsAsync(
             Resources::QP_COMP,
             'list'
         );
-        $this->addOptionalQueryParam(
-            $queryParams,
-            Resources::QP_PREFIX_LOWERCASE,
-            str_replace('\\', '/', $options->getPrefix())
-        );
+        if (null !== $options->getPrefix()) {
+            $this->addOptionalQueryParam(
+                $queryParams,
+                Resources::QP_PREFIX_LOWERCASE,
+                str_replace('\\', '/', $options->getPrefix())
+            );
+        }
         $this->addOptionalQueryParam(
             $queryParams,
             Resources::QP_MARKER_LOWERCASE,