diff --git a/hardware/arduino/sam/cores/arduino/itoa.c b/hardware/arduino/sam/cores/arduino/itoa.c
index fc3576602..ecd87f30c 100644
--- a/hardware/arduino/sam/cores/arduino/itoa.c
+++ b/hardware/arduino/sam/cores/arduino/itoa.c
@@ -121,7 +121,7 @@ extern char* ltoa( long value, char *string, int radix )
   return string;
 }
 
-extern char* utoa( unsigned long value, char *string, int radix )
+extern char* utoa( unsigned int value, char *string, int radix )
 {
   return ultoa( value, string, radix ) ;
 }
diff --git a/hardware/arduino/sam/cores/arduino/itoa.h b/hardware/arduino/sam/cores/arduino/itoa.h
index 59af10947..751c490b5 100644
--- a/hardware/arduino/sam/cores/arduino/itoa.h
+++ b/hardware/arduino/sam/cores/arduino/itoa.h
@@ -31,7 +31,7 @@ extern void itoa( int n, char s[] ) ;
 
 extern char* itoa( int value, char *string, int radix ) ;
 extern char* ltoa( long value, char *string, int radix ) ;
-extern char* utoa( unsigned long value, char *string, int radix ) ;
+extern char* utoa( unsigned int value, char *string, int radix ) ;
 extern char* ultoa( unsigned long value, char *string, int radix ) ;
 #endif /* 0 */
 
@@ -40,3 +40,4 @@ extern char* ultoa( unsigned long value, char *string, int radix ) ;
 #endif // __cplusplus
 
 #endif // _ITOA_
+