diff --git a/ports/esp32/mpconfigport.h b/ports/esp32/mpconfigport.h
index ea3487bcd8..4701040e66 100644
--- a/ports/esp32/mpconfigport.h
+++ b/ports/esp32/mpconfigport.h
@@ -91,6 +91,7 @@
 #define MICROPY_PY_UOS_INCLUDEFILE          "ports/esp32/moduos.c"
 #define MICROPY_PY_OS_DUPTERM               (1)
 #define MICROPY_PY_UOS_DUPTERM_NOTIFY       (1)
+#define MICROPY_PY_UOS_SYNC                 (1)
 #define MICROPY_PY_UOS_UNAME                (1)
 #define MICROPY_PY_UOS_URANDOM              (1)
 #define MICROPY_PY_MACHINE                  (1)
diff --git a/ports/esp8266/mpconfigport.h b/ports/esp8266/mpconfigport.h
index 12ea3716d4..0cfb83f73e 100644
--- a/ports/esp8266/mpconfigport.h
+++ b/ports/esp8266/mpconfigport.h
@@ -87,6 +87,7 @@
 #define MICROPY_PY_OS_DUPTERM       (2)
 #define MICROPY_PY_UOS_DUPTERM_NOTIFY (1)
 #define MICROPY_PY_UOS_DUPTERM_STREAM_DETACHED_ATTACHED (1)
+#define MICROPY_PY_UOS_SYNC         (1)
 #define MICROPY_PY_UOS_UNAME        (1)
 #define MICROPY_PY_UOS_UNAME_RELEASE_DYNAMIC (1)
 #define MICROPY_PY_UOS_URANDOM      (1)
diff --git a/ports/mimxrt/mpconfigport.h b/ports/mimxrt/mpconfigport.h
index 4482e54960..52301cf94b 100644
--- a/ports/mimxrt/mpconfigport.h
+++ b/ports/mimxrt/mpconfigport.h
@@ -76,6 +76,7 @@ uint32_t trng_random_u32(void);
 #define MICROPY_PY_UOS_INCLUDEFILE          "ports/mimxrt/moduos.c"
 #define MICROPY_PY_OS_DUPTERM               (3)
 #define MICROPY_PY_UOS_DUPTERM_NOTIFY       (1)
+#define MICROPY_PY_UOS_SYNC                 (1)
 #define MICROPY_PY_UOS_UNAME                (1)
 #define MICROPY_PY_UOS_URANDOM              (1)
 #define MICROPY_PY_URANDOM_SEED_INIT_FUNC   (trng_random_u32())
diff --git a/ports/rp2/mpconfigport.h b/ports/rp2/mpconfigport.h
index b4487a23d7..720e858f19 100644
--- a/ports/rp2/mpconfigport.h
+++ b/ports/rp2/mpconfigport.h
@@ -99,6 +99,7 @@
 #ifndef MICROPY_PY_OS_DUPTERM
 #define MICROPY_PY_OS_DUPTERM                   (1)
 #endif
+#define MICROPY_PY_UOS_SYNC                     (1)
 #define MICROPY_PY_UOS_UNAME                    (1)
 #define MICROPY_PY_UOS_URANDOM                  (1)
 #define MICROPY_PY_URE_MATCH_GROUPS             (1)
diff --git a/ports/samd/mcu/samd51/mpconfigmcu.h b/ports/samd/mcu/samd51/mpconfigmcu.h
index 07d4696901..0c2d2370ff 100644
--- a/ports/samd/mcu/samd51/mpconfigmcu.h
+++ b/ports/samd/mcu/samd51/mpconfigmcu.h
@@ -27,6 +27,7 @@
 
 #define MICROPY_PY_MACHINE_DHT_READINTO (1)
 #define MICROPY_PY_ONEWIRE              (1)
+#define MICROPY_PY_UOS_SYNC             (1)
 #define MICROPY_PY_UOS_URANDOM          (1)
 #define MICROPY_PY_URANDOM_SEED_INIT_FUNC (trng_random_u32())
 unsigned long trng_random_u32(void);