diff --git a/include/haproxy/tools.h b/include/haproxy/tools.h
index aa9fd777c..72bb5325e 100644
--- a/include/haproxy/tools.h
+++ b/include/haproxy/tools.h
@@ -642,7 +642,26 @@ extern time_t my_timegm(const struct tm *tm);
  * <ret> is left untouched.
  */
 extern const char *parse_time_err(const char *text, unsigned *ret, unsigned unit_flags);
-extern const char *parse_size_err(const char *text, unsigned *ret);
+extern const char *parse_size_ui(const char *text, unsigned *ret);
+extern const char *parse_size_ull(const char *text, ullong *ret);
+
+/* Parse a size from <_test> into <_ret> which must be compatible with a
+ * uint or ullong. The return value is a pointer to the first unparsable
+ * character (if any) or NULL if everything's OK.
+ */
+#define parse_size_err(_text, _ret) ({			\
+	const char *_err;				\
+	if (sizeof(*(_ret)) > sizeof(int)) {		\
+		unsigned long long _tmp;		\
+		_err = parse_size_ull(_text, &_tmp);	\
+		*_ret = _tmp;				\
+	} else {					\
+		unsigned int _tmp;			\
+		_err = parse_size_ui(_text, &_tmp);	\
+		*_ret = _tmp;				\
+	}						\
+	_err;						\
+})
 
 /*
  * Parse binary string written in hexadecimal (source) and store the decoded
diff --git a/src/tools.c b/src/tools.c
index d2decb69b..224c5df97 100644
--- a/src/tools.c
+++ b/src/tools.c
@@ -2780,7 +2780,8 @@ const char *parse_time_err(const char *text, unsigned *ret, unsigned unit_flags)
  * stored in <ret>. If an error is detected, the pointer to the unexpected
  * character is returned. If the conversion is successful, NULL is returned.
  */
-const char *parse_size_err(const char *text, unsigned *ret) {
+const char *parse_size_ui(const char *text, unsigned *ret)
+{
 	unsigned value = 0;
 
 	if (!isdigit((unsigned char)*text))
@@ -2833,6 +2834,76 @@ const char *parse_size_err(const char *text, unsigned *ret) {
 	return NULL;
 }
 
+/* this function converts the string starting at <text> to an ullong stored in
+ * <ret>. If an error is detected, the pointer to the unexpected character is
+ * returned. If the conversion is successful, NULL is returned.
+ */
+const char *parse_size_ull(const char *text, ullong *ret)
+{
+	ullong value = 0;
+
+	if (!isdigit((unsigned char)*text))
+		return text;
+
+	while (1) {
+		unsigned int j;
+
+		j = *text - '0';
+		if (j > 9)
+			break;
+		if (value > ~0ULL / 10)
+			return text;
+		value *= 10;
+		if (value > (value + j))
+			return text;
+		value += j;
+		text++;
+	}
+
+	switch (*text) {
+	case '\0':
+		break;
+	case 'K':
+	case 'k':
+		if (value > ~0ULL >> 10)
+			return text;
+		value = value << 10;
+		break;
+	case 'M':
+	case 'm':
+		if (value > ~0ULL >> 20)
+			return text;
+		value = value << 20;
+		break;
+	case 'G':
+	case 'g':
+		if (value > ~0ULL >> 30)
+			return text;
+		value = value << 30;
+		break;
+	case 'T':
+	case 't':
+		if (value > ~0ULL >> 40)
+			return text;
+		value = value << 40;
+		break;
+	case 'P':
+	case 'p':
+		if (value > ~0ULL >> 50)
+			return text;
+		value = value << 50;
+		break;
+	default:
+		return text;
+	}
+
+	if (*text != '\0' && *++text != '\0')
+		return text;
+
+	*ret = value;
+	return NULL;
+}
+
 /*
  * Parse binary string written in hexadecimal (source) and store the decoded
  * result into binstr and set binstrlen to the length of binstr. Memory for