diff --git a/libraries/DataFlash/LogStructure.h b/libraries/DataFlash/LogStructure.h
index 0f185efc9a..e6518ea7e3 100644
--- a/libraries/DataFlash/LogStructure.h
+++ b/libraries/DataFlash/LogStructure.h
@@ -92,6 +92,7 @@ const struct UnitStructure log_Units[] = {
     // { 'N', "N" },          // Newton
     { 'o', "m/s/s" },         // metres per second per second
     { 'O', "degC" },          // degrees Celsius. Not SI, but Kelvin is too cumbersome for most users
+    { '%', "%" },             // percent
     { 'S', "satellites" },    // number of satellites
     { 's', "s" },             // seconds
     { 'q', "rpm" },           // rounds per minute. Not SI, but sometimes more intuitive than Hertz