diff --git a/libraries/AP_HAL/Util.cpp b/libraries/AP_HAL/Util.cpp
index bdd18400de..2f9d25f6ee 100644
--- a/libraries/AP_HAL/Util.cpp
+++ b/libraries/AP_HAL/Util.cpp
@@ -24,7 +24,7 @@ int AP_HAL::Util::snprintf(char* str, size_t size, const char *format, ...)
 {
     va_list ap;
     va_start(ap, format);
-    int res = this->vsnprintf(str, size, format, ap);
+    int res = vsnprintf(str, size, format, ap);
     va_end(ap);
     return res;
 }
@@ -33,7 +33,7 @@ int AP_HAL::Util::snprintf_P(char* str, size_t size, const prog_char_t *format,
 {
     va_list ap;
     va_start(ap, format);
-    int res = this->vsnprintf_P(str, size, format, ap);
+    int res = vsnprintf_P(str, size, format, ap);
     va_end(ap);
     return res;
 }
@@ -44,8 +44,9 @@ int AP_HAL::Util::vsnprintf(char* str, size_t size, const char *format, va_list
     BufferPrinter buf(str, size);
     print_vprintf(&buf, 0, format, ap);
     // null terminate if possible
+    int ret = buf._offs;
     buf.write(0);
-    return (int) buf._offs;
+    return ret;
 }
 
 int AP_HAL::Util::vsnprintf_P(char* str, size_t size, const prog_char_t *format,
@@ -53,7 +54,8 @@ int AP_HAL::Util::vsnprintf_P(char* str, size_t size, const prog_char_t *format,
 {
     BufferPrinter buf(str, size);
     print_vprintf(&buf, 1,(const char*) format, ap);
+    int ret = buf._offs;
     // null terminate if possible
     buf.write(0);
-    return (int) buf._offs;
+    return ret;
 }
diff --git a/libraries/AP_HAL/examples/Printf/Printf.pde b/libraries/AP_HAL/examples/Printf/Printf.pde
index 7d3c0749e4..be5e6c1f97 100644
--- a/libraries/AP_HAL/examples/Printf/Printf.pde
+++ b/libraries/AP_HAL/examples/Printf/Printf.pde
@@ -35,17 +35,23 @@ static const struct {
     { "%f", 10.6f, "10.60000" },
     { "%f", 1020.4f, "1020.400" },
     { "%f", 1030.6f, "1030.600" },
-    { "%f", 10304052.6f, "1.0304053e+07" },
-    { "%f", 103040501.6f, "1.0304050e+08" },
-    { "%f", 1030405023.6f, "1.0304050e+09" },
+    { "%f", 10.123456f, "10.12346" },
+    { "%f", 102.123456f, "102.1235" },
+    { "%f", 1020.123456f, "1020.123" },
+    { "%.6f", 10.123456f, "10.12346" },
+    { "%.6f", 102.123456f, "102.1235" },
+    { "%.6f", 1020.123456f, "1020.123" },
+    { "%f", 10304052.6f, "1.030405e+07" },
+    { "%f", 103040501.6f, "1.030405e+08" },
+    { "%f", 1030405023.6f, "1.030405e+09" },
     { "%f", -1030.6f, "-1030.600" },
-    { "%f", -10304052.6f, "-1.0304053e+07" },
-    { "%f", -103040501.6f, "-1.0304050e+08" },
-    { "%f", -1030405023.6f, "-1.0304050e+09" },
-    { "%e", 103040501.6f, "1.0304050e+08" },
-    { "%g", 103040501.6f, "1.030405e+08" },
-    { "%e", -103040501.6f, "-1.0304050e+08" },
-    { "%g", -103040501.6f, "-1.030405e+08" },
+    { "%f", -10304052.6f, "-1.030405e+07" },
+    { "%f", -103040501.6f, "-1.030405e+08" },
+    { "%f", -1030405023.6f, "-1.030405e+09" },
+    { "%e", 103040501.6f, "1.030405e+08" },
+    { "%g", 103040501.6f, "1.03041e+08" },
+    { "%e", -103040501.6f, "-1.030405e+08" },
+    { "%g", -103040501.6f, "-1.03041e+08" },
     { "%.0f", 10.4f, "10" },
     { "%.0f", 10.6f, "11" },
     { "%.1f", 10.4f, "10.4" },
@@ -59,7 +65,7 @@ static void test_printf(void)
     uint8_t failures = 0;
     hal.console->printf("Running printf tests\n");
     for (i=0; i<sizeof(float_tests)/sizeof(float_tests[0]); i++) {
-        hal.util->snprintf(buf, sizeof(buf), float_tests[i].fmt, float_tests[i].v);
+        int ret = hal.util->snprintf(buf, sizeof(buf), float_tests[i].fmt, float_tests[i].v);
         if (strcmp(buf, float_tests[i].result) != 0) {
             hal.console->printf("Failed float_tests[%u] '%s' -> '%s' should be '%s'\n", 
                                 (unsigned)i, 
@@ -68,6 +74,14 @@ static void test_printf(void)
                                 float_tests[i].result);
             failures++;
         }
+        if (ret != strlen(float_tests[i].result)) {
+            hal.console->printf("Failed float_tests[%u] ret=%d/%d '%s' should be '%s'\n", 
+                                (unsigned)i, 
+                                ret, (int)strlen(float_tests[i].result),
+                                float_tests[i].fmt,
+                                float_tests[i].result);
+            failures++;            
+        }
     }
     hal.console->printf("%u failures\n", (unsigned)failures);
 }
diff --git a/libraries/AP_HAL/utility/print_vprintf.cpp b/libraries/AP_HAL/utility/print_vprintf.cpp
index 79f0603bd5..6cae4141e3 100644
--- a/libraries/AP_HAL/utility/print_vprintf.cpp
+++ b/libraries/AP_HAL/utility/print_vprintf.cpp
@@ -173,7 +173,7 @@ void print_vprintf (AP_HAL::Print *s, unsigned char in_progmem, const char *fmt,
                 flt_oper:
                         float value = va_arg(ap,double);
                         if (!(flags & FL_PREC))
-                                prec = 7;
+                                prec = 6;
                         flags &= ~(FL_FLTEXP | FL_FLTFIX);
                         if (c == 'e') {
                                 flags |= FL_FLTEXP;
@@ -284,7 +284,7 @@ void print_vprintf (AP_HAL::Print *s, unsigned char in_progmem, const char *fmt,
                                                 s->write('.');
                                         flags = (n <= exp && n > exp - ndigs)
                                                 ? buf[exp - n + 1] : '0';
-                                        if (--n < -prec)
+                                        if (--n < -prec || flags == 0)
                                                 break;
                                         s->write(flags);
                                 } while (1);
@@ -294,7 +294,7 @@ void print_vprintf (AP_HAL::Print *s, unsigned char in_progmem, const char *fmt,
                                         {
                                                 flags = '1';
                                         }
-                                s->write(flags);
+                                if (flags) s->write(flags);
         
                         } else {                                /* 'e(E)' format        */