diff --git a/src/functions/kern.js b/src/functions/kern.js
index 963f30f5..7c282290 100644
--- a/src/functions/kern.js
+++ b/src/functions/kern.js
@@ -48,7 +48,7 @@ defineFunction({
 
         if (group.value.dimension) {
             const dimension = calculateSize(group.value.dimension, options);
-            rule.style.marginLeft = dimension + "em";
+            rule.style.marginRight = dimension + "em";
         }
 
         return rule;
diff --git a/test/screenshotter/images/ModSpacing-chrome.png b/test/screenshotter/images/ModSpacing-chrome.png
new file mode 100644
index 00000000..7102f408
Binary files /dev/null and b/test/screenshotter/images/ModSpacing-chrome.png differ
diff --git a/test/screenshotter/images/ModSpacing-firefox.png b/test/screenshotter/images/ModSpacing-firefox.png
new file mode 100644
index 00000000..c94ecc94
Binary files /dev/null and b/test/screenshotter/images/ModSpacing-firefox.png differ
diff --git a/test/screenshotter/ss_data.yaml b/test/screenshotter/ss_data.yaml
index b0a3a44c..9655a67c 100644
--- a/test/screenshotter/ss_data.yaml
+++ b/test/screenshotter/ss_data.yaml
@@ -173,6 +173,12 @@ ModScript: |
         \scriptstyle a\bmod 2 & \scriptstyle b \pod 3 \\
         \scriptstyle c\pmod{4} & \scriptstyle d \mod{56}
     \end{array}
+ModSpacing: |
+    \begin{array}{l}
+        (a \cdot b) \bmod 257 \\
+        (a \cdot b) \mkern1mu\mathbin{\mathrm{mod}}\mkern1mu 257 \\
+        (a \cdot b) \mathbin{\mathrm{mod}} 257
+    \end{array}
 NegativeSpaceBetweenRel: A =\!= B
 NestedFractions: |
     \dfrac{\frac{a}{b}}{\frac{c}{d}}\dfrac{\dfrac{a}{b}}