diff --git a/libraries/AP_HAL/utility/print_vprintf.cpp b/libraries/AP_HAL/utility/print_vprintf.cpp
index 6cae4141e3..44c81aa82f 100644
--- a/libraries/AP_HAL/utility/print_vprintf.cpp
+++ b/libraries/AP_HAL/utility/print_vprintf.cpp
@@ -59,6 +59,7 @@
 #define FL_WIDTH	0x20
 #define FL_PREC		0x40
 #define FL_LONG		0x80
+#define FL_LONGLONG	0x100
 
 #define FL_PGMSTRING	FL_LONG
 #define FL_NEGATIVE	FL_LONG
@@ -73,10 +74,10 @@
 void print_vprintf (AP_HAL::Print *s, unsigned char in_progmem, const char *fmt, va_list ap)
 {
         unsigned char c;        /* holds a char from the format string */
-        unsigned char flags;
+        uint16_t flags;
         unsigned char width;
         unsigned char prec;
-        unsigned char buf[13];
+        unsigned char buf[23];
 
         for (;;) {
 
@@ -147,6 +148,9 @@ void print_vprintf (AP_HAL::Print *s, unsigned char in_progmem, const char *fmt,
                                 }
                                 if (c == 'h')
                                         continue;
+                        } else if ((flags & FL_LONG) && c == 'l') {
+                                flags |= FL_LONGLONG;
+                                continue;
                         }
             
                         break;
@@ -279,22 +283,23 @@ void print_vprintf (AP_HAL::Print *s, unsigned char in_progmem, const char *fmt,
                         if (flags & FL_FLTFIX) {                /* 'f' format           */
 
                                 n = exp > 0 ? exp : 0;          /* exponent of left digit */
+                                unsigned char v = 0;
                                 do {
                                         if (n == -1)
                                                 s->write('.');
-                                        flags = (n <= exp && n > exp - ndigs)
+                                        v = (n <= exp && n > exp - ndigs)
                                                 ? buf[exp - n + 1] : '0';
-                                        if (--n < -prec || flags == 0)
+                                        if (--n < -prec || v == 0)
                                                 break;
-                                        s->write(flags);
+                                        s->write(v);
                                 } while (1);
                                 if (n == exp
                                     && (buf[1] > '5'
                                         || (buf[1] == '5' && !(vtype & FTOA_CARRY))) )
                                         {
-                                                flags = '1';
+                                                v = '1';
                                         }
-                                if (flags) s->write(flags);
+                                if (v) s->write(v);
         
                         } else {                                /* 'e(E)' format        */
 
@@ -375,13 +380,23 @@ void print_vprintf (AP_HAL::Print *s, unsigned char in_progmem, const char *fmt,
                  * Handle integer formats variations for d/i, u, o, p, x, X.
                  */
                 if (c == 'd' || c == 'i') {
-                        long x = (flags & FL_LONG) ? va_arg(ap,long) : va_arg(ap,int);
-                        flags &= ~(FL_NEGATIVE | FL_ALT);
-                        if (x < 0) {
-                                x = -x;
-                                flags |= FL_NEGATIVE;
+                        if (flags & FL_LONGLONG) {
+                                int64_t x = va_arg(ap,long long);
+                                flags &= ~(FL_NEGATIVE | FL_ALT);
+                                if (x < 0) {
+                                        x = -x;
+                                        flags |= FL_NEGATIVE;
+                                }
+                                c = ulltoa_invert (x, (char *)buf, 10) - (char *)buf;
+                        } else {
+                                long x = (flags & FL_LONG) ? va_arg(ap,long) : va_arg(ap,int);
+                                flags &= ~(FL_NEGATIVE | FL_ALT);
+                                if (x < 0) {
+                                        x = -x;
+                                        flags |= FL_NEGATIVE;
+                                }
+                                c = ultoa_invert (x, (char *)buf, 10) - (char *)buf;
                         }
-                        c = ultoa_invert (x, (char *)buf, 10) - (char *)buf;
 
                 } else {
                         int base;
@@ -411,10 +426,15 @@ void print_vprintf (AP_HAL::Print *s, unsigned char in_progmem, const char *fmt,
                                         flags |= (FL_ALTHEX | FL_ALTUPP);
                                 base = 16 | XTOA_UPPER;
                         ultoa:
-                                c = ultoa_invert ((flags & FL_LONG)
-                                                    ? va_arg(ap, unsigned long)
-                                                    : va_arg(ap, unsigned int),
-                                                    (char *)buf, base)  -  (char *)buf;
+                                if (flags & FL_LONGLONG) {
+                                        c = ulltoa_invert (va_arg(ap, unsigned long long),
+                                                           (char *)buf, base)  -  (char *)buf;
+                                } else {
+                                        c = ultoa_invert ((flags & FL_LONG)
+                                                          ? va_arg(ap, unsigned long)
+                                                          : va_arg(ap, unsigned int),
+                                                          (char *)buf, base)  -  (char *)buf;
+                                }
                                 flags &= ~FL_NEGATIVE;
                                 break;
 
diff --git a/libraries/AP_HAL/utility/utoa_invert.cpp b/libraries/AP_HAL/utility/utoa_invert.cpp
index 0f8584e842..30eaecdff2 100644
--- a/libraries/AP_HAL/utility/utoa_invert.cpp
+++ b/libraries/AP_HAL/utility/utoa_invert.cpp
@@ -75,3 +75,49 @@ char * ultoa_invert (uint32_t val, char *s, uint8_t base) {
 	return s;
 }
 
+
+char * ulltoa_invert (uint64_t val, char *s, uint8_t base) {
+	if (base == 8) {
+		do {
+			*s = '0' + (val & 0x7);
+			val >>= 3;
+		} while(val);
+		return s;
+	}
+
+	if (base == 16) {
+		do {
+			uint8_t digit = '0' + (val & 0xf);
+#if XTOA_UPPER == 0
+			if (digit > '0' + 9)
+				digit += ('a' - '0' - 10);
+#else
+			if (digit > '0' + 9)
+				digit += ('A' - '0' - 10);
+#endif
+			*s++ = digit;
+			val >>= 4;
+		} while(val);
+		return s;
+	}
+
+	// Every base which in not hex and not oct is considered decimal.
+
+	// 64 bits is not actually enough, we need 65, but it should
+	// be good enough for the log dumping we're using this for
+	uint64_t xval = val;
+	do {
+		uint8_t saved = xval;
+		xval &= ~1;
+		xval += 2;
+		xval += xval >> 1;		// *1.5
+		xval += xval >> 4;		// *1.0625
+		xval += xval >> 8;		// *1.00390625
+		xval += xval >> 16;		// *1.000015259
+		xval += xval >> 32;		// it all amounts to *1.6
+		xval >>= 4;				// /16 ... so *1.6/16 is /10, fraction truncated.
+		*s++ = '0' + saved - 10 * (uint8_t)xval;
+	} while (xval);
+	return s;
+}
+
diff --git a/libraries/AP_HAL/utility/xtoa_fast.h b/libraries/AP_HAL/utility/xtoa_fast.h
index 024fd51eda..21462c7b2a 100644
--- a/libraries/AP_HAL/utility/xtoa_fast.h
+++ b/libraries/AP_HAL/utility/xtoa_fast.h
@@ -36,6 +36,7 @@
 
 /* Internal function for use from `printf'.	*/
 char *ultoa_invert (uint32_t val, char *s, uint8_t base);
+char *ulltoa_invert (uint64_t val, char *s, uint8_t base);
 
 /* Next flags are to use with `base'. Unused fields are reserved.	*/
 #define XTOA_PREFIX	0x0100	/* put prefix for octal or hex	*/