diff --git a/src/actions/action-creators.test.js b/src/actions/action-creators.test.js
index dd752b5..cdd477b 100644
--- a/src/actions/action-creators.test.js
+++ b/src/actions/action-creators.test.js
@@ -45,7 +45,10 @@ const desmosMock = {
   GraphingCalculator: jest.fn(() => {
     return {
       asyncScreenshot: (opts, cb) => cb(''),
-      getExpressions: () => [{ id: 1, latex: 'x = 3' }, { id: 2, latex: '' }],
+      getExpressions: () => [
+        { id: 1, type: 'expression', latex: 'x = 3' },
+        { id: 2, latex: '' }
+      ],
       setExpression: () => null
     };
   })
diff --git a/src/lib/calc-helpers.js b/src/lib/calc-helpers.js
index 42957f9..d88b5c8 100644
--- a/src/lib/calc-helpers.js
+++ b/src/lib/calc-helpers.js
@@ -28,10 +28,14 @@ export const getImageData = opts =>
  */
 const getExpByIndex = idx => calculator.getExpressions()[idx - 1];
 
-// Returns an error message on failure.
+/**
+ * Returns an error message on failure.
+ * Skips expressions that are not of type 'expression'
+ */
 export const setSliderByIndex = (idx, val) => {
   const exp = getExpByIndex(idx);
   if (!exp) return noSuchExpression(idx);
+  if (exp.type !== 'expression') return notASlider(idx);
 
   const { id, latex } = exp;
   const match = latex.match(/(.+)=/);