diff --git a/src/main/blackbox/blackbox_io.c b/src/main/blackbox/blackbox_io.c
index 835777725..ddf9c5905 100644
--- a/src/main/blackbox/blackbox_io.c
+++ b/src/main/blackbox/blackbox_io.c
@@ -91,12 +91,13 @@ static void _putc(void *p, char c)
 }
 
 //printf() to the blackbox serial port with no blocking shenanigans (so it's caller's responsibility to not write too fast!)
-void blackboxPrintf(char *fmt, ...)
+int blackboxPrintf(const char *fmt, ...)
 {
     va_list va;
     va_start(va, fmt);
-    tfp_format(NULL, _putc, fmt, va);
+    int written = tfp_format(NULL, _putc, fmt, va);
     va_end(va);
+    return written;
 }
 
 // Print the null-terminated string 's' to the serial port and return the number of bytes written
diff --git a/src/main/blackbox/blackbox_io.h b/src/main/blackbox/blackbox_io.h
index 547850739..1cc2b654e 100644
--- a/src/main/blackbox/blackbox_io.h
+++ b/src/main/blackbox/blackbox_io.h
@@ -36,7 +36,7 @@ uint8_t blackboxWriteChunkSize;
 
 void blackboxWrite(uint8_t value);
 
-void blackboxPrintf(char *fmt, ...);
+int blackboxPrintf(const char *fmt, ...);
 int blackboxPrint(const char *s);
 
 void blackboxWriteUnsignedVB(uint32_t value);