diff --git a/src/XmlRpcClient.cpp b/src/XmlRpcClient.cpp
index b264c4b..ea53646 100644
--- a/src/XmlRpcClient.cpp
+++ b/src/XmlRpcClient.cpp
@@ -252,7 +252,7 @@ XmlRpcClient::generateHeader(std::string const& body)
   header += buff;
   header += "Content-Type: text/xml\r\nContent-length: ";
 
-  sprintf(buff,"%d\r\n\r\n", body.size());
+  sprintf(buff,"%d\r\n\r\n", (int)body.size());
 
   return header + buff;
 }
diff --git a/src/XmlRpcServerConnection.cpp b/src/XmlRpcServerConnection.cpp
index 4386e72..515a199 100644
--- a/src/XmlRpcServerConnection.cpp
+++ b/src/XmlRpcServerConnection.cpp
@@ -348,7 +348,7 @@ XmlRpcServerConnection::generateHeader(std::string const& body)
     "Content-length: ";
 
   char buffLen[40];
-  sprintf(buffLen,"%d\r\n\r\n", body.size());
+  sprintf(buffLen,"%d\r\n\r\n", (int)body.size());
 
   return header + buffLen;
 }