diff --git a/cores/esp32/MD5Builder.cpp b/cores/esp32/MD5Builder.cpp
index c988abd1e05..e242c3763b9 100644
--- a/cores/esp32/MD5Builder.cpp
+++ b/cores/esp32/MD5Builder.cpp
@@ -78,6 +78,7 @@ bool MD5Builder::addStream(Stream & stream, const size_t maxLen)
         // read data and check if we got something
         int numBytesRead = stream.readBytes(buf, readBytes);
         if(numBytesRead< 1) {
+            free(buf);
             return false;
         }