diff --git a/accounting.js b/accounting.js
index fd181fd..fe3ee62 100644
--- a/accounting.js
+++ b/accounting.js
@@ -156,6 +156,17 @@
 				zero : defaults
 			};
 
+		// If format is an object then neg and zero should be optional
+		} else if ( isObject( format ) && ( !format.neg || !format.zero ) ) {
+
+			// If the negative or zero value is missing, populate based on positive
+			if ( !format.neg ) {
+				format.neg = format.pos.replace("%v", "-%v");
+			}
+			if ( !format.zero ) {
+				format.zero = format.pos;
+			}
+
 		}
 		// Otherwise, assume format was fine:
 		return format;
diff --git a/tests/qunit/methods.js b/tests/qunit/methods.js
index 19e354b..4d56566 100644
--- a/tests/qunit/methods.js
+++ b/tests/qunit/methods.js
@@ -58,6 +58,7 @@ $(document).ready(function() {
 		equals(accounting.formatMoney(0, { symbol: "GBP",  format:format}), "GBP  --", "`format` parameter provided given as an object with `zero` format, correctly observed in string output");
 		equals(accounting.formatMoney(-1000, { symbol: "GBP",  format:format}), "GBP (1,000.00)", "`format` parameter provided given as an object with `neg` format, correctly observed in string output");
 		equals(accounting.formatMoney(1000, { symbol: "GBP",  format:{neg:"--%v %s"}}), "GBP1,000.00", "`format` parameter provided, but only `neg` value provided - positive value should be formatted by default format (%s%v)");
+		equals(accounting.formatMoney(-1000, { symbol: "GBP",  format:{pos:"%s%v"}}), "GBP-1,000.00", "`format` parameter provided, but only `pos` value provided - negative and zero should be optional");
 		
 		accounting.settings.currency.format = "%s%v";
 		accounting.formatMoney(0, {format:""});