diff --git a/Parser.js b/Parser.js
index ff4798707..fdce97e2e 100644
--- a/Parser.js
+++ b/Parser.js
@@ -289,6 +289,7 @@ var copyFuncs = {
         "\\nleq"
     ],
     "spacing": [
+        "\\!",
         "\\ ",
         "\\,",
         "\\:",
diff --git a/buildTree.js b/buildTree.js
index 42d9587b1..e05bd70cb 100644
--- a/buildTree.js
+++ b/buildTree.js
@@ -287,7 +287,8 @@ var groupTypes = {
                 "\\quad": "quad",
                 "\\;": "thickspace",
                 "\\:": "mediumspace",
-                "\\,": "thinspace"
+                "\\,": "thinspace",
+                "\\!": "negativethinspace"
             };
 
             return makeSpan(["mord", "mspace", spacingClassMap[group.value]]);
diff --git a/static/katex.less b/static/katex.less
index 03ad4cafd..fa2489c4d 100644
--- a/static/katex.less
+++ b/static/katex.less
@@ -232,6 +232,10 @@ big parens
     .mspace {
         display: inline-block;
 
+        &.negativethinspace {
+            margin-left: -@thinspace;
+        }        
+
         &.thinspace {
             width: @thinspace;
         }