diff --git a/cores/arduino/avr/dtostrf.c b/cores/arduino/avr/dtostrf.c
index 259caa5b3..de164277b 100644
--- a/cores/arduino/avr/dtostrf.c
+++ b/cores/arduino/avr/dtostrf.c
@@ -20,6 +20,8 @@
 #include <stdio.h>
 
 char *dtostrf (double val, signed char width, unsigned char prec, char *sout) {
+  asm(".global _printf_float");
+
   char fmt[20];
   sprintf(fmt, "%%%d.%df", width, prec);
   sprintf(sout, fmt, val);