diff --git a/src/Curl/MultiCurl.php b/src/Curl/MultiCurl.php
index 6f8a5fa..b70b695 100644
--- a/src/Curl/MultiCurl.php
+++ b/src/Curl/MultiCurl.php
@@ -639,7 +639,13 @@ class MultiCurl
         }
 
         do {
-            curl_multi_select($this->multiCurl);
+
+            // Wait for activity on any curl_multi connection when curl_multi_select (libcurl) fails to correctly block.
+            // https://bugs.php.net/bug.php?id=63411
+            if (curl_multi_select($this->multiCurl) === -1) {
+                usleep(100000);
+            }
+
             curl_multi_exec($this->multiCurl, $active);
 
             while (!($info_array = curl_multi_info_read($this->multiCurl)) === false) {