diff --git a/src/JSON.cc b/src/JSON.cc
index ed2e4949..c225b5e8 100644
--- a/src/JSON.cc
+++ b/src/JSON.cc
@@ -22,7 +22,6 @@
 ////////////////////
 
 std::mutex JSON::_token;
-bool JSON::Parser::firstCall = true;
 
 
 ///////////////////////////////////
@@ -1777,17 +1776,6 @@ Initialize the JSON parser given an input stream \p _is.
 */
 JSON::Parser::Parser(std::istream& _is)
 {
-    // On first call, switch off syncing between C++ and C I/O. This call must
-    // be done before first I/O operation as the behavior may be undefined
-    // otherwise.
-    if (firstCall)
-    {
-        firstCall = false;
-        //  Don't sync C++ and C I/O
-        // from http://www.manticmoo.com/articles/jeff/programming/c++/making-io-streams-efficient-in-c++.php
-        std::ios_base::sync_with_stdio(false);
-    }
-
     while (_is)
     {
         std::string input_line;
diff --git a/src/JSON.h b/src/JSON.h
index 14ca857c..5d512fc4 100644
--- a/src/JSON.h
+++ b/src/JSON.h
@@ -432,10 +432,6 @@ class JSON
         char _current {};
         /// the position inside the input buffer
         size_t _pos = 0;
-
-      private:
-        /// variable to guard std::ios_base::sync_with_stdio
-        static bool firstCall;
     };
 };