diff --git a/devtools/test_dashboard/test_gl3d.js b/devtools/test_dashboard/test_gl3d.js
index 76ed41e6379..f6e92ca314a 100644
--- a/devtools/test_dashboard/test_gl3d.js
+++ b/devtools/test_dashboard/test_gl3d.js
@@ -26,7 +26,7 @@ plots['triangle-mesh3d'] = require('@mocks/gl3d_triangle.json');
 plots['snowden'] = require('@mocks/gl3d_snowden.json');
 plots['bunny'] = require('@mocks/gl3d_bunny.json');
 plots['ribbons'] = require('@mocks/gl3d_ribbons.json');
-plots['date-time'] = require('@mocks/gl3d_scatter-date.json');
+plots['scatter-time'] = require('@mocks/gl3d_scatter-date.json');
 plots['cufflinks'] = require('@mocks/gl3d_cufflinks.json');
 plots['chrisp-nan-1'] = require('@mocks/gl3d_chrisp-nan-1.json');
 plots['marker-arrays'] = require('@mocks/gl3d_marker-arrays.json');
diff --git a/src/traces/scatter3d/attributes.js b/src/traces/scatter3d/attributes.js
index 4d392baa2e4..4c3a155196d 100644
--- a/src/traces/scatter3d/attributes.js
+++ b/src/traces/scatter3d/attributes.js
@@ -114,7 +114,17 @@ module.exports = {
         sizeref: scatterMarkerAttrs.sizeref,
         sizemin: scatterMarkerAttrs.sizemin,
         sizemode: scatterMarkerAttrs.sizemode,
-        opacity: scatterMarkerAttrs.opacity,
+        opacity: extendFlat({}, scatterMarkerAttrs.opacity, {
+            arrayOk: false,
+            description: [
+                'Sets the marker opacity.',
+                'Note that the marker opacity for scatter3d traces',
+                'must be a scalar value for performance reasons.',
+                'To set a blending opacity value',
+                '(i.e. which is not transparent), set *marker.color*',
+                'to an rgba color and use its alpha channel.'
+            ].join(' ')
+        }),
         colorscale: scatterMarkerAttrs.colorscale,
         cauto: scatterMarkerAttrs.cauto,
         cmax: scatterMarkerAttrs.cmax,
diff --git a/src/traces/scatter3d/convert.js b/src/traces/scatter3d/convert.js
index 6bd61f5d8ad..c6fd15f59e7 100644
--- a/src/traces/scatter3d/convert.js
+++ b/src/traces/scatter3d/convert.js
@@ -319,10 +319,9 @@ proto.update = function(data) {
         this.linePlot = null;
     }
 
+    // N.B. marker.opacity must be a scalar for performance
     var scatterOpacity = data.opacity;
-    if(data.marker && typeof data.marker.opacity === 'number') {
-      scatterOpacity *= data.marker.opacity;
-    }
+    if(data.marker && data.marker.opacity) scatterOpacity *= data.marker.opacity;
 
     scatterOptions = {
         gl:           gl,