diff --git a/src/plots/cartesian/set_convert.js b/src/plots/cartesian/set_convert.js
index a7d28d24655..2070dc30cb6 100644
--- a/src/plots/cartesian/set_convert.js
+++ b/src/plots/cartesian/set_convert.js
@@ -184,10 +184,13 @@ module.exports = function setConvert(ax) {
             // that aren't in the first etc.
             // TODO: sorting options - do the sorting
             // progressively here as we insert?
-            if(ax._categories.indexOf(v)===-1) ax._categories.push(v);
+
+            if(v !== null && v !== undefined && ax._categories.indexOf(v) === -1){
+                ax._categories.push(v);
+            }
 
             var c = ax._categories.indexOf(v);
-            return c===-1 ? constants.BADNUM : c;
+            return c === -1 ? constants.BADNUM : c;
         };
 
         ax.d2l = ax.d2c;
diff --git a/test/image/baselines/axes_category_null.png b/test/image/baselines/axes_category_null.png
new file mode 100644
index 00000000000..bc75883b8fc
Binary files /dev/null and b/test/image/baselines/axes_category_null.png differ
diff --git a/test/image/mocks/axes_category_null.json b/test/image/mocks/axes_category_null.json
new file mode 100644
index 00000000000..1dff64f4b46
--- /dev/null
+++ b/test/image/mocks/axes_category_null.json
@@ -0,0 +1,44 @@
+{
+    "data": [
+        {
+            "x": [
+                1,
+                2,
+                null,
+                4,
+                5
+            ],
+            "y": [
+                1,
+                2,
+                3,
+                4,
+                5
+            ],
+            "connectgaps": false,
+            "uid": "8ac13a"
+        }
+    ],
+    "layout": {
+        "title": "null categories",
+        "xaxis": {
+            "type": "category",
+            "range": [
+                -0.18336673346693386,
+                3.1833667334669338
+            ],
+            "autorange": true
+        },
+        "yaxis": {
+            "type": "linear",
+            "range": [
+                0.7070063694267517,
+                5.292993630573249
+            ],
+            "autorange": true
+        },
+        "height": 450,
+        "width": 1000,
+        "autosize": true
+    }
+}
diff --git a/test/jasmine/tests/calcdata_test.js b/test/jasmine/tests/calcdata_test.js
new file mode 100644
index 00000000000..df134e774cc
--- /dev/null
+++ b/test/jasmine/tests/calcdata_test.js
@@ -0,0 +1,31 @@
+var Plotly = require('@lib/index');
+
+var createGraphDiv = require('../assets/create_graph_div');
+var destroyGraphDiv = require('../assets/destroy_graph_div');
+
+describe('calculated data and points', function() {
+    describe('connectGaps', function() {
+
+        var gd;
+
+        beforeEach(function() {
+            gd = createGraphDiv();
+        });
+
+        afterEach(destroyGraphDiv);
+
+        it('should exclude null and undefined points when false', function() {
+            Plotly.plot(gd, [{ x: [1,2,3,undefined,5], y: [1,null,3,4,5]}], {});
+
+            expect(gd.calcdata[0][1]).toEqual({ x: false, y: false});
+            expect(gd.calcdata[0][3]).toEqual({ x: false, y: false});
+        });
+
+        it('should exclude null and undefined points as categories when false', function() {
+            Plotly.plot(gd, [{ x: [1,2,3,undefined,5], y: [1,null,3,4,5] }], { xaxis: { type: 'category' }});
+
+            expect(gd.calcdata[0][1]).toEqual({ x: false, y: false});
+            expect(gd.calcdata[0][3]).toEqual({ x: false, y: false});
+        });
+    });
+});