diff --git a/sys/include/usb/usbus/cdc/acm.h b/sys/include/usb/usbus/cdc/acm.h
index c558fecf5460..244d7b06a157 100644
--- a/sys/include/usb/usbus/cdc/acm.h
+++ b/sys/include/usb/usbus/cdc/acm.h
@@ -41,6 +41,8 @@
  */
 
 #include <stdint.h>
+#include <unistd.h>
+
 #include "usb/cdc.h"
 #include "usb/usbus.h"
 #include "tsrb.h"
@@ -198,9 +200,10 @@ void usbus_cdc_acm_init(usbus_t *usbus, usbus_cdcacm_device_t *cdcacm,
  * @param[in]   buf         buffer to submit
  * @param[in]   len         length of the submitted buffer
  *
- * @return                  Number of bytes added to the CDC ACM ring buffer
+ * @retval      -ECONNRESET Failed to submit data
+ * @retval      >=0         Number of bytes added to the CDC ACM ring buffer
  */
-size_t usbus_cdc_acm_submit(usbus_cdcacm_device_t *cdcacm,
+ssize_t usbus_cdc_acm_submit(usbus_cdcacm_device_t *cdcacm,
                            const uint8_t *buf, size_t len);
 
 /**
diff --git a/sys/picolibc_syscalls_default/syscalls.c b/sys/picolibc_syscalls_default/syscalls.c
index 8277f3ba97f6..0849df03f841 100644
--- a/sys/picolibc_syscalls_default/syscalls.c
+++ b/sys/picolibc_syscalls_default/syscalls.c
@@ -180,10 +180,19 @@ static int picolibc_stdout_queued;
 
 static void _picolibc_flush(void)
 {
-    if (picolibc_stdout_queued) {
-        stdio_write(picolibc_stdout, picolibc_stdout_queued);
-        picolibc_stdout_queued = 0;
+    char *pos = picolibc_stdout;
+    char *end = pos + picolibc_stdout_queued;
+    while (pos < end) {
+        size_t left = (size_t)end - (size_t)pos;
+        ssize_t written = stdio_write(pos, left);
+        if (written < 0) {
+            /* failed to flush, drop data */
+            break;
+        }
+        pos += written;
     }
+
+    picolibc_stdout_queued = 0;
 }
 
 static int picolibc_put(char c, FILE *file)
diff --git a/sys/usb/usbus/cdc/acm/cdc_acm.c b/sys/usb/usbus/cdc/acm/cdc_acm.c
index 4c9b347f1515..b91872be93de 100644
--- a/sys/usb/usbus/cdc/acm/cdc_acm.c
+++ b/sys/usb/usbus/cdc/acm/cdc_acm.c
@@ -19,6 +19,7 @@
 #define USB_H_USER_IS_RIOT_INTERNAL
 
 #include <assert.h>
+#include <errno.h>
 #include <string.h>
 
 #include "tsrb.h"
@@ -148,12 +149,12 @@ static size_t _gen_full_acm_descriptor(usbus_t *usbus, void *arg)
 }
 
 /* Submit (ACM interface in) */
-size_t usbus_cdc_acm_submit(usbus_cdcacm_device_t *cdcacm, const uint8_t *buf, size_t len)
+ssize_t usbus_cdc_acm_submit(usbus_cdcacm_device_t *cdcacm, const uint8_t *buf, size_t len)
 {
-    size_t n;
+    ssize_t n;
     unsigned old;
     if (cdcacm->state == USBUS_CDC_ACM_LINE_STATE_DISCONNECTED) {
-        return len;
+        return -ECONNRESET;
     }
 
     old = irq_disable();
diff --git a/sys/usb/usbus/cdc/acm/cdc_acm_stdio.c b/sys/usb/usbus/cdc/acm/cdc_acm_stdio.c
index 64ab9bb1d700..ac1c8f3abcfe 100644
--- a/sys/usb/usbus/cdc/acm/cdc_acm_stdio.c
+++ b/sys/usb/usbus/cdc/acm/cdc_acm_stdio.c
@@ -24,7 +24,6 @@
 #include <stdio.h>
 #include <sys/types.h>
 
-#include "log.h"
 #include "isrpipe.h"
 #include "stdio_base.h"
 
@@ -36,15 +35,9 @@ static uint8_t _cdc_tx_buf_mem[CONFIG_USBUS_CDC_ACM_STDIO_BUF_SIZE];
 
 static ssize_t _write(const void* buffer, size_t len)
 {
-    const char *start = buffer;
-    while (len) {
-        size_t n = usbus_cdc_acm_submit(&cdcacm, buffer, len);
-        usbus_cdc_acm_flush(&cdcacm);
-        /* Use tsrb and flush */
-        buffer = (char *)buffer + n;
-        len -= n;
-    }
-    return (char *)buffer - start;
+    ssize_t retval = usbus_cdc_acm_submit(&cdcacm, buffer, len);
+    usbus_cdc_acm_flush(&cdcacm);
+    return retval;
 }
 
 static void _cdc_acm_rx_pipe(usbus_cdcacm_device_t *cdcacm,