diff --git a/include/common/standard.h b/include/common/standard.h
index d8b56b68d..4808a2285 100644
--- a/include/common/standard.h
+++ b/include/common/standard.h
@@ -64,10 +64,29 @@
 extern int strlcpy2(char *dst, const char *src, int size);
 
 /*
- * This function simply returns a statically allocated string containing
+ * This function simply returns a locally allocated string containing
  * the ascii representation for number 'n' in decimal.
  */
-extern char *ultoa(unsigned long n);
+extern char itoa_str[][21];
+extern const char *ultoa_r(unsigned long n, char *buffer, int size);
+static inline const char *ultoa(unsigned long n)
+{
+	return ultoa_r(n, itoa_str[0], sizeof(itoa_str[0]));
+}
+
+/* Fast macros to convert up to 10 different parameters inside a same call of
+ * expression.
+ */
+#define U2A0(n) ({ ultoa_r((n), itoa_str[0], sizeof(itoa_str[0])); })
+#define U2A1(n) ({ ultoa_r((n), itoa_str[1], sizeof(itoa_str[1])); })
+#define U2A2(n) ({ ultoa_r((n), itoa_str[2], sizeof(itoa_str[2])); })
+#define U2A3(n) ({ ultoa_r((n), itoa_str[3], sizeof(itoa_str[3])); })
+#define U2A4(n) ({ ultoa_r((n), itoa_str[4], sizeof(itoa_str[4])); })
+#define U2A5(n) ({ ultoa_r((n), itoa_str[5], sizeof(itoa_str[5])); })
+#define U2A6(n) ({ ultoa_r((n), itoa_str[6], sizeof(itoa_str[6])); })
+#define U2A7(n) ({ ultoa_r((n), itoa_str[7], sizeof(itoa_str[7])); })
+#define U2A8(n) ({ ultoa_r((n), itoa_str[8], sizeof(itoa_str[8])); })
+#define U2A9(n) ({ ultoa_r((n), itoa_str[9], sizeof(itoa_str[9])); })
 
 /*
  * Returns non-zero if character <s> is a hex digit (0-9, a-f, A-F), else zero.
diff --git a/src/standard.c b/src/standard.c
index 80e0d1b4a..fff7168ca 100644
--- a/src/standard.c
+++ b/src/standard.c
@@ -20,8 +20,11 @@
 #include <common/standard.h>
 #include <proto/log.h>
 
-/* enough to store 2^64-1 = 18446744073709551615 */
-static char itoa_str[21];
+/* enough to store 10 integers of :
+ *   2^64-1 = 18446744073709551615 or
+ *    -2^63 = -9223372036854775808
+ */
+char itoa_str[10][21];
 
 /*
  * copies at most <size-1> chars from <src> to <dst>. Last char is always
@@ -43,20 +46,20 @@ int strlcpy2(char *dst, const char *src, int size)
 }
 
 /*
- * This function simply returns a statically allocated string containing
+ * This function simply returns a locally allocated string containing
  * the ascii representation for number 'n' in decimal.
  */
-char *ultoa(unsigned long n)
+const char *ultoa_r(unsigned long n, char *buffer, int size)
 {
 	char *pos;
 	
-	pos = itoa_str + sizeof(itoa_str) - 1;
+	pos = buffer + size - 1;
 	*pos-- = '\0';
 	
 	do {
 		*pos-- = '0' + n % 10;
 		n /= 10;
-	} while (n && pos >= itoa_str);
+	} while (n && pos >= buffer);
 	return pos + 1;
 }