diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
index 6555f1f511c..ac511fcee52 100644
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -7050,8 +7050,10 @@ posix_unsetenv(PyObject *self, PyObject *args)
         return NULL;
 
     err = unsetenv(s1);
-    if (err)
+    if (err) {
+        Py_DECREF(s1);
         return posix_error();
+    }
 
     /* Remove the key from posix_putenv_garbage;
      * this will cause it to be collected.  This has to