diff --git a/Modules/_testcapi/abstract.c b/Modules/_testcapi/abstract.c
index 38236aaf4f4..1c4c45c6c93 100644
--- a/Modules/_testcapi/abstract.c
+++ b/Modules/_testcapi/abstract.c
@@ -1,5 +1,3 @@
-#include <stddef.h>               // ptrdiff_t
-
 #define PY_SSIZE_T_CLEAN
 #include "parts.h"
 #include "util.h"
diff --git a/Modules/_testcapi/dict.c b/Modules/_testcapi/dict.c
index 374464c40d5..41c8dfde0da 100644
--- a/Modules/_testcapi/dict.c
+++ b/Modules/_testcapi/dict.c
@@ -1,5 +1,3 @@
-#include <stddef.h>               // ptrdiff_t
-
 #define PY_SSIZE_T_CLEAN
 #include "parts.h"
 #include "util.h"
diff --git a/Modules/_testcapi/set.c b/Modules/_testcapi/set.c
index 3c58f185638..2fbd0aeffcd 100644
--- a/Modules/_testcapi/set.c
+++ b/Modules/_testcapi/set.c
@@ -1,5 +1,3 @@
-#include <stddef.h>               // ptrdiff_t
-
 #include "parts.h"
 #include "util.h"