diff --git a/edge/format.js b/edge/format.js
index 70e2720..1f701f2 100644
--- a/edge/format.js
+++ b/edge/format.js
@@ -528,6 +528,11 @@ function format(content, options = {}) {
 				outputBuffer.append('{')
 			}
 
+			const parentIsArithmeticOperator = inputNode.parent instanceof Stylus.nodes.UnaryOp || inputNode.parent instanceof Stylus.nodes.BinOp && inputNode.parent.left === inputNode
+			if (parentIsArithmeticOperator) {
+				outputBuffer.append(openParen)
+			}
+
 			const currentIsPartOfPropertyNames = !!findParentNode(inputNode, node => node instanceof Stylus.nodes.Property && node.segments.includes(inputNode))
 
 			const currentIsPartOfKeyframes = !!findParentNode(inputNode, node => node instanceof Stylus.nodes.Keyframes && node.segments.includes(inputNode))
@@ -558,6 +563,10 @@ function format(content, options = {}) {
 				outputBuffer.append('}')
 			}
 
+			if (parentIsArithmeticOperator) {
+				outputBuffer.append(closeParen)
+			}
+
 			if (insideExpression === false) {
 				if (options.insertSemicolons) {
 					outputBuffer.append(';')
@@ -601,9 +610,8 @@ function format(content, options = {}) {
 				outputBuffer.append(travel(inputNode, inputNode.val, indentLevel, true))
 
 			} else {
-				const insideUnaryOp = inputNode.parent instanceof Stylus.nodes.Expression && (inputNode.parent.parent instanceof Stylus.nodes.UnaryOp || inputNode.parent.parent instanceof Stylus.nodes.BinOp)
 				const escapeDivider = inputNode.op === '/'
-				if (insideUnaryOp || escapeDivider) {
+				if (escapeDivider) {
 					outputBuffer.append(openParen)
 				}
 
@@ -613,7 +621,7 @@ function format(content, options = {}) {
 					outputBuffer.append(' ' + travel(inputNode, inputNode.right, indentLevel, true))
 				}
 
-				if (insideUnaryOp || escapeDivider) {
+				if (escapeDivider) {
 					outputBuffer.append(closeParen)
 				}
 			}
diff --git a/spec/operator/input.styl b/spec/operator/input.styl
index 3fe0603..a4a91d0 100644
--- a/spec/operator/input.styl
+++ b/spec/operator/input.styl
@@ -1,11 +1,14 @@
 body
   display !0
   visibility not true is false
-  left -5px
-  margin 1+2px
+  margin-top -5px
+  margin-bottom -(6px)
+  margin-left value
+  margin-right -(value)
+  padding 1+2px
   list = 1 2 3
   color 1 in list
-  padding list[-1]
+  item = list[-1]
   range = 1...5
   math = 1+2- 3*(4/5) %6**7
   color = color is defined ? unit(num,'px') : white
diff --git a/spec/operator/output.styl b/spec/operator/output.styl
index 4202756..9f8fe99 100644
--- a/spec/operator/output.styl
+++ b/spec/operator/output.styl
@@ -1,11 +1,14 @@
 body {
 	display: !0;
 	visibility: !true == false;
-	left: -5px;
-	margin: 1 + 2px;
+	margin-top: -5px;
+	margin-bottom: -(6px);
+	margin-left: value;
+	margin-right: -(value);
+	padding: 1 + 2px;
 	list = 1 2 3;
 	color: 1 in list;
-	padding: list[-1];
+	item = list[-1];
 	range = 1...5;
 	math = 1 + 2 - 3 * (4 / 5) % 6 ** 7;
 	color = color is defined ? unit(num, 'px') : white;