diff --git a/run_tests.py b/run_tests.py
index 71c31bf..5087111 100755
--- a/run_tests.py
+++ b/run_tests.py
@@ -21,4 +21,4 @@
     "run_mesonui_tests.py",
 ]
 
-check_call(cmd, encoding="utf8", stderr=STDOUT)
+check_call(cmd, encoding="utf-8", stderr=STDOUT)