 ext/mbstring/oniguruma/src/config.h.win32 | 1 +
 ext/mbstring/oniguruma/src/config.h.win64 | 1 +
 2 files changed, 2 insertions(+)

diff --git a/ext/mbstring/oniguruma/src/config.h.win32 b/ext/mbstring/oniguruma/src/config.h.win32
index bdbdaf25c1..9a9c43f26d 100644
--- a/ext/mbstring/oniguruma/src/config.h.win32
+++ b/ext/mbstring/oniguruma/src/config.h.win32
@@ -15,6 +15,7 @@
 #define SIZEOF_VOIDP 4
 #define SIZEOF_FLOAT 4
 #define SIZEOF_DOUBLE 8
+#define SIZEOF_SIZE_T 4
 #define HAVE_PROTOTYPES 1
 #define TOKEN_PASTE(x,y) x##y
 #define HAVE_STDARG_PROTOTYPES 1
diff --git a/ext/mbstring/oniguruma/src/config.h.win64 b/ext/mbstring/oniguruma/src/config.h.win64
index 01a86c7bb9..dec7b75773 100644
--- a/ext/mbstring/oniguruma/src/config.h.win64
+++ b/ext/mbstring/oniguruma/src/config.h.win64
@@ -15,6 +15,7 @@
 #define SIZEOF_VOIDP 8
 #define SIZEOF_FLOAT 4
 #define SIZEOF_DOUBLE 8
+#define SIZEOF_SIZE_T 8
 #define HAVE_PROTOTYPES 1
 #define TOKEN_PASTE(x,y) x##y
 #define HAVE_STDARG_PROTOTYPES 1
