diff --git a/spintrum/spintrum.py b/spintrum/spintrum.py
index 58d73b3..43104d3 100644
--- a/spintrum/spintrum.py
+++ b/spintrum/spintrum.py
@@ -8,6 +8,7 @@ import mpmath
 
 def _print_error(msg_str):
     sys.stderr.write(msg_str + "\n")
+    sys.stderr.flush()
 
 
 try: