diff --git a/superset-frontend/plugins/legacy-plugin-chart-heatmap/src/Heatmap.js b/superset-frontend/plugins/legacy-plugin-chart-heatmap/src/Heatmap.js
index dc442039112e7..b0b32aba4a1ac 100644
--- a/superset-frontend/plugins/legacy-plugin-chart-heatmap/src/Heatmap.js
+++ b/superset-frontend/plugins/legacy-plugin-chart-heatmap/src/Heatmap.js
@@ -111,7 +111,7 @@ function Heatmap(element, props) {
   let showY = true;
   let showX = true;
   const pixelsPerCharX = 4.5; // approx, depends on font size
-  const pixelsPerCharY = 6; // approx, depends on font size
+  let pixelsPerCharY = 6; // approx, depends on font size
 
   const valueFormatter = getNumberFormatter(numberFormat);
 
@@ -121,6 +121,7 @@ function Heatmap(element, props) {
     let longestY = 1;
 
     records.forEach(datum => {
+      if (typeof datum.y === 'number') pixelsPerCharY = 7;
       longestX = Math.max(
         longestX,
         (datum.x && datum.x.toString().length) || 1,