diff --git a/lib/compressor/compress/Attribute.js b/lib/compressor/compress/Attribute.js
index 3940ce3f..99cafdce 100644
--- a/lib/compressor/compress/Attribute.js
+++ b/lib/compressor/compress/Attribute.js
@@ -5,7 +5,7 @@ var escapesRx = /\\([0-9A-Fa-f]{1,6})[ \t\n\f\r]?|\\./g;
 var blockUnquoteRx = /^(-?\d|--)|[\u0000-\u002c\u002e\u002f\u003A-\u0040\u005B-\u005E\u0060\u007B-\u009f]/;
 
 function canUnquote(value) {
-    if (!value) {
+    if (value === '' || value === '-') {
         return;
     }
 
diff --git a/test/fixture/compress/attrib.string/1.css b/test/fixture/compress/attrib.string/1.css
index bac589c6..894fbc1c 100644
--- a/test/fixture/compress/attrib.string/1.css
+++ b/test/fixture/compress/attrib.string/1.css
@@ -1,6 +1,7 @@
 [title="test"],
 [title="123"],
 [title="test test"],
+[title="-"],
 [title=""]
 {
     p: v;
diff --git a/test/fixture/compress/attrib.string/1.min.css b/test/fixture/compress/attrib.string/1.min.css
index 683f6e51..6c93b1f2 100644
--- a/test/fixture/compress/attrib.string/1.min.css
+++ b/test/fixture/compress/attrib.string/1.min.css
@@ -1 +1 @@
-[title=""],[title="123"],[title="test test"],[title=test]{p:v}
+[title=""],[title="-"],[title="123"],[title="test test"],[title=test]{p:v}
diff --git a/test/fixture/compress/attrib.string/2.css b/test/fixture/compress/attrib.string/2.css
index a069f992..0393d463 100644
--- a/test/fixture/compress/attrib.string/2.css
+++ b/test/fixture/compress/attrib.string/2.css
@@ -1,6 +1,7 @@
 [title='test'],
 [title='123'],
 [title='test test'],
+[title='-'],
 [title='']
 {
     p: v;
diff --git a/test/fixture/compress/attrib.string/2.min.css b/test/fixture/compress/attrib.string/2.min.css
index 5be10c74..7e7e838a 100644
--- a/test/fixture/compress/attrib.string/2.min.css
+++ b/test/fixture/compress/attrib.string/2.min.css
@@ -1 +1 @@
-[title=''],[title='123'],[title='test test'],[title=test]{p:v}
+[title=''],[title='-'],[title='123'],[title='test test'],[title=test]{p:v}