diff --git a/include/pybind11/iostream.h b/include/pybind11/iostream.h
index 7f34bb2010f..29cfae9ee7d 100644
--- a/include/pybind11/iostream.h
+++ b/include/pybind11/iostream.h
@@ -52,9 +52,12 @@ class pythonbuf : public std::streambuf {
 
                 pywrite(line);
                 pyflush();
+
+                // Placed inside gil_scoped_aquire as a makeshift mutex
+                // to reduce MSVC issues
+                setp(pbase(), epptr());
             }
 
-            setp(pbase(), epptr());
         }
         return 0;
     }