diff --git a/include/pybind11/eval.h b/include/pybind11/eval.h
index a588729182..ee24fd3584 100644
--- a/include/pybind11/eval.h
+++ b/include/pybind11/eval.h
@@ -52,9 +52,8 @@ object eval(const str &expr, object global = globals(), object local = object())
 
     detail::ensure_builtins_in_globals(global);
 
-    /* PyRun_String does not accept a PyObject / encoding specifier,
-       this seems to be the only alternative */
-    std::string buffer = "# -*- coding: utf-8 -*-\n" + (std::string) expr;
+    // PyRun_String requires a plain C string; Python 3 always assumes UTF-8 source.
+    std::string buffer = (std::string) expr;
 
     int start = 0;
     switch (mode) {