diff --git a/draftlogs/5956_add.md b/draftlogs/5956_add.md
index c790a7cb13f..7382acb7659 100644
--- a/draftlogs/5956_add.md
+++ b/draftlogs/5956_add.md
@@ -1,2 +1,2 @@
- - Add `smith` subplots and the `scattersmith` trace type for displaying Smith charts [[#5956](https://github.com/plotly/plotly.js/pull/5956)],
+ - Add `smith` subplots and the `scattersmith` trace type for displaying Smith charts [[#5956](https://github.com/plotly/plotly.js/pull/5956), [#5992](https://github.com/plotly/plotly.js/pull/5992)],
    with thanks to Kitware and @waxlamp for kicking off this effort.
diff --git a/src/plots/smith/layout_defaults.js b/src/plots/smith/layout_defaults.js
index fc332959a41..1a36a46dd59 100644
--- a/src/plots/smith/layout_defaults.js
+++ b/src/plots/smith/layout_defaults.js
@@ -16,6 +16,12 @@ var layoutAttributes = require('./layout_attributes');
 var constants = require('./constants');
 var axisNames = constants.axisNames;
 
+var makeImagDflt = memoize(function(realTickvals) {
+    return realTickvals.slice().reverse().map(function(x) { return -x; })
+        .concat([0])
+        .concat(realTickvals);
+}, String);
+
 function handleDefaults(contIn, contOut, coerce, opts) {
     var bgColor = coerce('bgcolor');
     opts.bgColor = Color.combine(bgColor, opts.paper_bgcolor);
@@ -55,11 +61,10 @@ function handleDefaults(contIn, contOut, coerce, opts) {
             if(isRealAxis) {
                 coerceAxis('tickvals');
             } else {
-                var realTickvals = contOut.realaxis.tickvals || layoutAttributes.realaxis.tickvals.dflt;
-                var imagTickvalsDflt =
-                    realTickvals.slice().reverse().map(function(x) { return -x; })
-                    .concat([0])
-                    .concat(realTickvals);
+                var imagTickvalsDflt = makeImagDflt(
+                    contOut.realaxis.tickvals ||
+                    layoutAttributes.realaxis.tickvals.dflt
+                );
 
                 coerceAxis('tickvals', imagTickvalsDflt);
             }
@@ -132,3 +137,15 @@ module.exports = function supplyLayoutDefaults(layoutIn, layoutOut, fullData) {
         layoutOut: layoutOut
     });
 };
+
+function memoize(fn, keyFn) {
+    var cache = {};
+    return function(val) {
+        var newKey = keyFn ? keyFn(val) : val;
+        if(newKey in cache) { return cache[newKey]; }
+
+        var out = fn(val);
+        cache[newKey] = out;
+        return out;
+    };
+}