diff --git a/src/WebSockets.cpp b/src/WebSockets.cpp
index 21d3ef8..100ce79 100644
--- a/src/WebSockets.cpp
+++ b/src/WebSockets.cpp
@@ -595,7 +595,7 @@ bool WebSockets::readCb(WSclient_t * client, uint8_t * out, size_t n, WSreadWait
 
 #else
     unsigned long t = millis();
-    size_t len;
+    ssize_t len;
     DEBUG_WEBSOCKETS("[readCb] n: %zu t: %lu\n", n, t);
     while(n > 0) {
         if(client->tcp == NULL) {
@@ -633,7 +633,7 @@ bool WebSockets::readCb(WSclient_t * client, uint8_t * out, size_t n, WSreadWait
         }
 
         len = client->tcp->read((uint8_t *)out, n);
-        if(len) {
+        if(len > 0) {
             t = millis();
             out += len;
             n -= len;