diff --git a/src/buildHTML.js b/src/buildHTML.js
index 759c319fd..11faf4088 100644
--- a/src/buildHTML.js
+++ b/src/buildHTML.js
@@ -42,7 +42,7 @@ var groupToType = {
     open: "mopen",
     close: "mclose",
     inner: "minner",
-    genfrac: "minner",
+    genfrac: "mord",
     array: "minner",
     spacing: "mord",
     punct: "mpunct",
@@ -155,6 +155,14 @@ var isCharacterBox = function(group) {
         baseElem.type === "punct";
 };
 
+var makeNullDelimiter = function(options) {
+    return makeSpan([
+        "sizing", "reset-" + options.size, "size5",
+        options.style.reset(), Style.TEXT.cls(),
+        "nulldelimiter"
+    ]);
+};
+
 /**
  * This is a map of group types to the function used to handle that type.
  * Simpler types come at the beginning, while complicated types come afterwards.
@@ -469,8 +477,6 @@ var groupTypes = {
         frac.depth *= fstyle.sizeMultiplier / options.style.sizeMultiplier;
 
         // Rule 15e
-        var innerChildren = [makeSpan(["mfrac"], [frac])];
-
         var delimSize;
         if (fstyle.size === Style.DISPLAY.size) {
             delimSize = fontMetrics.metrics.delim1;
@@ -478,24 +484,25 @@ var groupTypes = {
             delimSize = fontMetrics.metrics.getDelim2(fstyle);
         }
 
-        if (group.value.leftDelim != null) {
-            innerChildren.unshift(
-                delimiter.customSizedDelim(
-                    group.value.leftDelim, delimSize, true,
-                    options.withStyle(fstyle), group.mode)
-            );
+        var leftDelim, rightDelim;
+        if (group.value.leftDelim == null) {
+            leftDelim = makeNullDelimiter(options);
+        } else {
+            leftDelim = delimiter.customSizedDelim(
+                group.value.leftDelim, delimSize, true,
+                options.withStyle(fstyle), group.mode);
         }
-        if (group.value.rightDelim != null) {
-            innerChildren.push(
-                delimiter.customSizedDelim(
-                    group.value.rightDelim, delimSize, true,
-                    options.withStyle(fstyle), group.mode)
-            );
+        if (group.value.rightDelim == null) {
+            rightDelim = makeNullDelimiter(options);
+        } else {
+            rightDelim = delimiter.customSizedDelim(
+                group.value.rightDelim, delimSize, true,
+                options.withStyle(fstyle), group.mode);
         }
 
         return makeSpan(
-            ["minner", options.style.reset(), fstyle.cls()],
-            innerChildren,
+            ["mord", options.style.reset(), fstyle.cls()],
+            [leftDelim, makeSpan(["mfrac"], [frac]), rightDelim],
             options.getColor());
     },
 
@@ -1035,7 +1042,7 @@ var groupTypes = {
         var leftDelim;
         if (group.value.left === ".") {
             // Empty delimiters in \left and \right make null delimiter spaces.
-            leftDelim = makeSpan(["nulldelimiter"]);
+            leftDelim = makeNullDelimiter(options);
         } else {
             // Otherwise, use leftRightDelim to generate the correct sized
             // delimiter.
@@ -1049,7 +1056,7 @@ var groupTypes = {
         var rightDelim;
         // Same for the right delimiter
         if (group.value.right === ".") {
-            rightDelim = makeSpan(["nulldelimiter"]);
+            rightDelim = makeNullDelimiter(options);
         } else {
             rightDelim = delimiter.leftRightDelim(
                 group.value.right, innerHeight, innerDepth, options,
diff --git a/test/screenshotter/images/Arrays-firefox.png b/test/screenshotter/images/Arrays-firefox.png
index bdec8ec52..9f963254d 100644
Binary files a/test/screenshotter/images/Arrays-firefox.png and b/test/screenshotter/images/Arrays-firefox.png differ
diff --git a/test/screenshotter/images/BinomTest-firefox.png b/test/screenshotter/images/BinomTest-firefox.png
index 4673810ef..7712db1a5 100644
Binary files a/test/screenshotter/images/BinomTest-firefox.png and b/test/screenshotter/images/BinomTest-firefox.png differ
diff --git a/test/screenshotter/images/DeepFontSizing-firefox.png b/test/screenshotter/images/DeepFontSizing-firefox.png
index c97970031..ea0aa2782 100644
Binary files a/test/screenshotter/images/DeepFontSizing-firefox.png and b/test/screenshotter/images/DeepFontSizing-firefox.png differ
diff --git a/test/screenshotter/images/DisplayMode-firefox.png b/test/screenshotter/images/DisplayMode-firefox.png
index baa1fdf41..913b1717d 100644
Binary files a/test/screenshotter/images/DisplayMode-firefox.png and b/test/screenshotter/images/DisplayMode-firefox.png differ
diff --git a/test/screenshotter/images/DisplayStyle-firefox.png b/test/screenshotter/images/DisplayStyle-firefox.png
index d6a468532..f5c59c4e1 100644
Binary files a/test/screenshotter/images/DisplayStyle-firefox.png and b/test/screenshotter/images/DisplayStyle-firefox.png differ
diff --git a/test/screenshotter/images/FractionTest-firefox.png b/test/screenshotter/images/FractionTest-firefox.png
index cbd953541..8c25211be 100644
Binary files a/test/screenshotter/images/FractionTest-firefox.png and b/test/screenshotter/images/FractionTest-firefox.png differ
diff --git a/test/screenshotter/images/NestedFractions-firefox.png b/test/screenshotter/images/NestedFractions-firefox.png
index 8d7a83ebc..b3607db1f 100644
Binary files a/test/screenshotter/images/NestedFractions-firefox.png and b/test/screenshotter/images/NestedFractions-firefox.png differ
diff --git a/test/screenshotter/images/Phantom-firefox.png b/test/screenshotter/images/Phantom-firefox.png
index 363cd2463..d0b92957c 100644
Binary files a/test/screenshotter/images/Phantom-firefox.png and b/test/screenshotter/images/Phantom-firefox.png differ
diff --git a/test/screenshotter/images/RlapBug-firefox.png b/test/screenshotter/images/RlapBug-firefox.png
index a31ce594c..ae96ebccf 100644
Binary files a/test/screenshotter/images/RlapBug-firefox.png and b/test/screenshotter/images/RlapBug-firefox.png differ
diff --git a/test/screenshotter/images/Text-firefox.png b/test/screenshotter/images/Text-firefox.png
index 688d7e83e..b43fcfc7c 100644
Binary files a/test/screenshotter/images/Text-firefox.png and b/test/screenshotter/images/Text-firefox.png differ
diff --git a/test/screenshotter/ss_data.json b/test/screenshotter/ss_data.json
index e3e214892..e5f9359f2 100644
--- a/test/screenshotter/ss_data.json
+++ b/test/screenshotter/ss_data.json
@@ -11,7 +11,7 @@
     "DisplayMode": "http://localhost:7936/test/screenshotter/test.html?m=\\sum_{i=0}^\\infty \\frac{1}{i}&pre=pre&post=post&display=1",
     "DisplayStyle": "http://localhost:7936/test/screenshotter/test.html?m={\\displaystyle\\sqrt{x}}{\\sqrt{x}}{\\displaystyle \\frac12}{\\frac12}{\\displaystyle x^1_2}{x^1_2}",
     "Exponents": "http://localhost:7936/test/screenshotter/test.html?m=a^{a^a_a}_{a^a_a}",
-    "FractionTest": "http://localhost:7936/test/screenshotter/test.html?m=\\dfrac{a}{b}\\frac{a}{b}\\tfrac{a}{b}",
+    "FractionTest": "http://localhost:7936/test/screenshotter/test.html?m=\\dfrac{a}{b}\\frac{a}{b}\\tfrac{a}{b}\\;-\\dfrac12\\;1\\tfrac12",
     "Functions": "http://localhost:7936/test/screenshotter/test.html?m=\\sin\\cos\\tan\\ln\\log",
     "GreekLetters": "http://localhost:7936/test/screenshotter/test.html?m=\\alpha\\beta\\gamma\\omega",
     "KaTeX": "http://localhost:7936/test/screenshotter/test.html?m=\\KaTeX",