Issue #27895:  Spelling fixes (Contributed by Ville Skyttä).
diff --git a/Modules/_testcapimodule.c b/Modules/_testcapimodule.c
index 3810e94..81f5b1d 100644
--- a/Modules/_testcapimodule.c
+++ b/Modules/_testcapimodule.c
@@ -3781,7 +3781,7 @@
 {
     PyThreadState *tstate = PyThreadState_GET();
 
-    /* substract one to ignore the frame of the get_recursion_depth() call */
+    /* subtract one to ignore the frame of the get_recursion_depth() call */
     return PyLong_FromLong(tstate->recursion_depth - 1);
 }