diff --git a/Python/_warnings.c b/Python/_warnings.c
index 331ad6c..6a970bb 100644
--- a/Python/_warnings.c
+++ b/Python/_warnings.c
@@ -377,7 +377,7 @@
         }
     }
 
-    if (rc == 1)  // Already warned for this module. */
+    if (rc == 1)  /* Already warned for this module. */
         goto return_none;
     if (rc == 0) {
         PyObject *show_fxn = get_warnings_attr("showwarning");
@@ -800,8 +800,8 @@
         warn_doc},
     {"warn_explicit", (PyCFunction)warnings_warn_explicit,
         METH_VARARGS | METH_KEYWORDS, warn_explicit_doc},
-    // XXX(brett.cannon): add showwarning?
-    // XXX(brett.cannon): Reasonable to add formatwarning?
+    /* XXX(brett.cannon): add showwarning? */
+    /* XXX(brett.cannon): Reasonable to add formatwarning? */
     {NULL, NULL}	        /* sentinel */
 };