diff --git a/spec/app/language-mode-spec.coffee b/spec/app/language-mode-spec.coffee
index adcd9b868..08a37fca7 100644
--- a/spec/app/language-mode-spec.coffee
+++ b/spec/app/language-mode-spec.coffee
@@ -28,6 +28,27 @@ describe "LanguageMode", ->
         expect(buffer.lineForRow(6)).toBe "//       current < pivot ? left.push(current) : right.push(current);"
         expect(buffer.lineForRow(7)).toBe "//     }"
 
+      it "only uncomments lines if all lines start with a comment", ->
+        languageMode.toggleLineCommentsForBufferRows(0, 0)
+        expect(buffer.lineForRow(0)).toBe "// var quicksort = function () {"
+
+        languageMode.toggleLineCommentsForBufferRows(0, 2)
+        expect(buffer.lineForRow(0)).toBe "// // var quicksort = function () {"
+        expect(buffer.lineForRow(1)).toBe "//   var sort = function(items) {"
+        expect(buffer.lineForRow(2)).toBe "//     if (items.length <= 1) return items;"
+
+      it "uncomments commented lines separated by an empty line", ->
+        languageMode.toggleLineCommentsForBufferRows(0, 1)
+        expect(buffer.lineForRow(0)).toBe "// var quicksort = function () {"
+        expect(buffer.lineForRow(1)).toBe "//   var sort = function(items) {"
+
+        buffer.insert([0, Infinity], '\n')
+
+        languageMode.toggleLineCommentsForBufferRows(0, 2)
+        expect(buffer.lineForRow(0)).toBe "var quicksort = function () {"
+        expect(buffer.lineForRow(1)).toBe ""
+        expect(buffer.lineForRow(2)).toBe "  var sort = function(items) {"
+
     describe "fold suggestion", ->
       describe ".doesBufferRowStartFold(bufferRow)", ->
         it "returns true only when the buffer row starts a foldable region", ->
diff --git a/src/app/language-mode.coffee b/src/app/language-mode.coffee
index ad1965fe8..b3cfb1ec9 100644
--- a/src/app/language-mode.coffee
+++ b/src/app/language-mode.coffee
@@ -64,6 +64,10 @@ class LanguageMode
           buffer.insert([start, 0], commentStartString)
           buffer.insert([end, buffer.lineLengthForRow(end)], commentEndString)
     else
+      if shouldUncomment and start isnt end
+        shouldUncomment = [start+1..end].every (row) ->
+          line = buffer.lineForRow(row)
+          not line or commentStartRegex.test(line)
       if shouldUncomment
         for row in [start..end]
           if match = commentStartRegex.search(buffer.lineForRow(row))