diff --git a/superset/assets/spec/javascripts/explore/AdhocFilter_spec.js b/superset/assets/spec/javascripts/explore/AdhocFilter_spec.js
index 0cf9e58e1f310..36d3bdd09552d 100644
--- a/superset/assets/spec/javascripts/explore/AdhocFilter_spec.js
+++ b/superset/assets/spec/javascripts/explore/AdhocFilter_spec.js
@@ -112,6 +112,26 @@ describe('AdhocFilter', () => {
     });
     // eslint-disable-next-line no-unused-expressions
     expect(adhocFilter3.isValid()).to.be.false;
+
+    const adhocFilter4 = new AdhocFilter({
+      expressionType: EXPRESSION_TYPES.SIMPLE,
+      subject: 'value',
+      operator: 'in',
+      comparator: [],
+      clause: CLAUSES.WHERE,
+    });
+    // eslint-disable-next-line no-unused-expressions
+    expect(adhocFilter4.isValid()).to.be.false;
+
+    const adhocFilter5 = new AdhocFilter({
+      expressionType: EXPRESSION_TYPES.SIMPLE,
+      subject: 'value',
+      operator: 'in',
+      comparator: ['val1'],
+      clause: CLAUSES.WHERE,
+    });
+    // eslint-disable-next-line no-unused-expressions
+    expect(adhocFilter5.isValid()).to.be.true;
   });
 
   it('can translate from simple expressions to sql expressions', () => {
diff --git a/superset/assets/src/explore/AdhocFilter.js b/superset/assets/src/explore/AdhocFilter.js
index 675cc27f613eb..7f1bdd019579f 100644
--- a/superset/assets/src/explore/AdhocFilter.js
+++ b/superset/assets/src/explore/AdhocFilter.js
@@ -83,7 +83,13 @@ export default class AdhocFilter {
 
   isValid() {
     if (this.expressionType === EXPRESSION_TYPES.SIMPLE) {
-      return !!(this.operator && this.subject && this.comparator && this.clause);
+      return !!(
+        this.operator &&
+        this.subject &&
+        this.comparator &&
+        this.comparator.length > 0 &&
+        this.clause
+      );
     } else if (this.expressionType === EXPRESSION_TYPES.SQL) {
       return !!(this.sqlExpression && this.clause);
     }