diff --git a/assets/javascripts/discourse/components/param-input.hbs b/assets/javascripts/discourse/components/param-input.hbs
index 6b1553e..5e9448f 100644
--- a/assets/javascripts/discourse/components/param-input.hbs
+++ b/assets/javascripts/discourse/components/param-input.hbs
@@ -64,6 +64,14 @@
     />
     <span class="param-name">{{@info.identifier}}</span>
 
+  {{else if (eq this.type "category_id")}}
+    <CategoryChooser
+      @value={{this.value}}
+      @onChange={{this.updateValue}}
+      name={{@info.identifier}}
+    />
+    <span class="param-name">{{@info.identifier}}</span>
+
   {{else}}
     <TextField
       @value={{this.value}}
diff --git a/assets/javascripts/discourse/components/param-input.js b/assets/javascripts/discourse/components/param-input.js
index 2a1d218..a00f0b7 100644
--- a/assets/javascripts/discourse/components/param-input.js
+++ b/assets/javascripts/discourse/components/param-input.js
@@ -19,7 +19,7 @@ const layoutMap = {
   user_id: "user_id",
   post_id: "string",
   topic_id: "generic",
-  category_id: "generic",
+  category_id: "category_id",
   group_id: "generic",
   badge_id: "generic",
   int_list: "generic",
@@ -62,24 +62,27 @@ export default class ParamInput extends Component {
           this.args.updateParams(this.args.info.identifier, this.boolValue);
         }
       } else {
-        this.value =
-          this.args.info.type === "category_id"
-            ? this.dasherizeCategoryId(initialValue)
-            : initialValue;
+        this.value = this.normalizeValue(initialValue);
         this.args.updateParams(this.args.info.identifier, this.value);
       }
     } else {
       // if no parsed params then get and set default values
       const defaultValue = this.args.info.default;
-      this.value =
-        this.args.info.type === "category_id"
-          ? this.dasherizeCategoryId(defaultValue)
-          : defaultValue;
+      this.value = this.normalizeValue(defaultValue);
       this.boolValue = defaultValue !== "false";
       this.nullableBoolValue = defaultValue;
     }
   }
 
+  normalizeValue(value) {
+    switch (this.args.info.type) {
+      case "category_id":
+        return this.digitalizeCategoryId(value);
+      default:
+        return value;
+    }
+  }
+
   get type() {
     const type = this.args.info.type;
     if ((type === "time" || type === "date") && !allowsInputTypeTime()) {
@@ -135,18 +138,8 @@ export default class ParamInput extends Component {
       case "category_id":
         if (isPositiveInt) {
           return !!this.site.categories.find((c) => c.id === intVal);
-        } else if (/\//.test(value)) {
-          const match = /(.*)\/(.*)/.exec(value);
-          if (!match) {
-            return false;
-          }
-          const result = Category.findBySlug(
-            dasherize(match[2]),
-            dasherize(match[1])
-          );
-          return !!result;
         } else {
-          return !!Category.findBySlug(dasherize(value));
+          return false;
         }
       case "group_id":
         const groups = this.site.get("groups");
@@ -163,13 +156,25 @@ export default class ParamInput extends Component {
     return this.site.get("groups");
   }
 
-  dasherizeCategoryId(value) {
+  digitalizeCategoryId(value) {
     value = String(value || "");
     const isPositiveInt = /^\d+$/.test(value);
-    if (!isPositiveInt && value !== dasherize(value)) {
-      return dasherize(value);
+    if (!isPositiveInt) {
+      if (/\//.test(value)) {
+        const match = /(.*)\/(.*)/.exec(value);
+        if (!match) {
+          value = null;
+        } else {
+          value = Category.findBySlug(
+            dasherize(match[2]),
+            dasherize(match[1])
+          )?.id;
+        }
+      } else {
+        value = Category.findBySlug(dasherize(value))?.id;
+      }
     }
-    return value;
+    return value?.toString();
   }
 
   @action
@@ -177,12 +182,9 @@ export default class ParamInput extends Component {
     // handle selectKit inputs as well as traditional inputs
     const value = input.target ? input.target.value : input;
     if (value.length) {
-      this.value =
-        this.args.info.type === "category_id"
-          ? this.dasherizeCategoryId(value.toString())
-          : value.toString();
+      this.value = this.normalizeValue(value.toString());
     } else {
-      this.value = value;
+      this.value = this.normalizeValue(value);
     }
 
     this.args.updateParams(this.args.info.identifier, this.value);
diff --git a/spec/system/param_input_spec.rb b/spec/system/param_input_spec.rb
index d93def2..8902aa6 100644
--- a/spec/system/param_input_spec.rb
+++ b/spec/system/param_input_spec.rb
@@ -63,6 +63,12 @@ RSpec.describe "Param input", type: :system, js: true do
 
     ::DiscourseDataExplorer::Parameter
       .create_from_sql(ALL_PARAMS_SQL)
-      .each { |param| expect(page).to have_css(".query-params [name=\"#{param.identifier}\"]") }
+      .each do |param|
+        if !param.nullable && param.type != :boolean && param.default.nil?
+          expect(page).to have_css(".query-params .param.invalid [name=\"#{param.identifier}\"]")
+        else
+          expect(page).to have_css(".query-params .param.valid [name=\"#{param.identifier}\"]")
+        end
+      end
   end
 end
diff --git a/test/javascripts/components/param-input-test.js b/test/javascripts/components/param-input-test.js
new file mode 100644
index 0000000..7203388
--- /dev/null
+++ b/test/javascripts/components/param-input-test.js
@@ -0,0 +1,42 @@
+import { render } from "@ember/test-helpers";
+import hbs from "htmlbars-inline-precompile";
+import { module, test } from "qunit";
+import { setupRenderingTest } from "discourse/tests/helpers/component-test";
+import selectKit from "discourse/tests/helpers/select-kit-helper";
+
+const values = {};
+function updateParams(identifier, value) {
+  values[identifier] = value;
+}
+
+module("Data Explorer Plugin | Component | param-input", function (hooks) {
+  setupRenderingTest(hooks);
+
+  test("Renders the categroy_id type correctly", async function (assert) {
+    this.setProperties({
+      info: {
+        identifier: "category_id",
+        type: "category_id",
+        default: null,
+        nullable: false,
+      },
+      initialValues: {},
+      params: {},
+      updateParams,
+    });
+
+    await render(hbs`<ParamInput
+      @params={{this.params}}
+      @initialValues={{this.initialValues}}
+      @info={{this.info}}
+      @updateParams={{this.updateParams}}
+    />`);
+
+    const categoryChooser = selectKit(".category-chooser");
+
+    await categoryChooser.expand();
+    await categoryChooser.selectRowByValue(2);
+
+    assert.strictEqual(values.category_id, "2");
+  });
+});