diff --git a/src/core/data_map.ts b/src/core/data_map.ts
index 35480678..5f970aef 100644
--- a/src/core/data_map.ts
+++ b/src/core/data_map.ts
@@ -43,6 +43,6 @@ export class DataMap {
   }
 
   getAttributeNameForKey(key: string): string {
-    return `data-${this.identifier}-${dasherize(key)}`
+    return `data-${this.identifier.toLowerCase()}-${dasherize(key)}`
   }
 }
diff --git a/src/tests/modules/core/value_tests_case_insensitive.ts b/src/tests/modules/core/value_tests_case_insensitive.ts
new file mode 100644
index 00000000..3efdb4ff
--- /dev/null
+++ b/src/tests/modules/core/value_tests_case_insensitive.ts
@@ -0,0 +1,92 @@
+import ValueTests from "./value_tests"
+
+export default class ValueCaseInsensitiveTests extends ValueTests {
+  identifier = "Test"
+
+  fixtureHTML = `
+    <div data-controller="${this.identifier}"
+      data-${this.identifier}-shadowed-boolean-value="true"
+      data-${this.identifier}-numeric-value="123"
+      data-${this.identifier}-string-value="ok"
+      data-${this.identifier}-ids-value="[1,2,3]"
+      data-${this.identifier}-options-value='{"one":[2,3]}'
+      data-${this.identifier}-time-24hr-value="true">
+    </div>
+  `
+
+  async "test changed callbacks"() {
+    this.assert.deepEqual(this.controller.loggedNumericValues, [123])
+    this.assert.deepEqual(this.controller.oldLoggedNumericValues, [0])
+
+    this.controller.numericValue = 0
+    await this.nextFrame
+    this.assert.deepEqual(this.controller.loggedNumericValues, [123, 0])
+    this.assert.deepEqual(this.controller.oldLoggedNumericValues, [0, 123])
+
+    this.set("numeric-value", "1")
+    await this.nextFrame
+    this.assert.deepEqual(this.controller.loggedNumericValues, [123, 0, 1])
+    this.assert.deepEqual(this.controller.oldLoggedNumericValues, [0, 123, 0])
+  }
+
+  async "test changed callbacks for object"() {
+    this.assert.deepEqual(this.controller.optionsValues, [{ one: [2, 3] }])
+    this.assert.deepEqual(this.controller.oldOptionsValues, [{}])
+
+    this.controller.optionsValue = { person: { name: "John", age: 42, active: true } }
+    await this.nextFrame
+    this.assert.deepEqual(this.controller.optionsValues, [
+      { one: [2, 3] },
+      { person: { name: "John", age: 42, active: true } },
+    ])
+    this.assert.deepEqual(this.controller.oldOptionsValues, [{}, { one: [2, 3] }])
+
+    this.set("options-value", "{}")
+    await this.nextFrame
+    this.assert.deepEqual(this.controller.optionsValues, [
+      { one: [2, 3] },
+      { person: { name: "John", age: 42, active: true } },
+      {},
+    ])
+    this.assert.deepEqual(this.controller.oldOptionsValues, [
+      {},
+      { one: [2, 3] },
+      { person: { name: "John", age: 42, active: true } },
+    ])
+  }
+
+  async "test default values trigger changed callbacks"() {
+    this.assert.deepEqual(this.controller.loggedMissingStringValues, [""])
+    this.assert.deepEqual(this.controller.oldLoggedMissingStringValues, [undefined])
+
+    this.controller.missingStringValue = "hello"
+    await this.nextFrame
+    this.assert.deepEqual(this.controller.loggedMissingStringValues, ["", "hello"])
+    this.assert.deepEqual(this.controller.oldLoggedMissingStringValues, [undefined, ""])
+
+    this.controller.missingStringValue = undefined as any
+    await this.nextFrame
+    this.assert.deepEqual(this.controller.loggedMissingStringValues, ["", "hello", ""])
+    this.assert.deepEqual(this.controller.oldLoggedMissingStringValues, [undefined, "", "hello"])
+  }
+
+  has(name: string) {
+    return this.element.hasAttribute(this.attr(name))
+  }
+
+  get(name: string) {
+    return this.element.getAttribute(this.attr(name))
+  }
+
+  set(name: string, value: string) {
+    return this.element.setAttribute(this.attr(name), value)
+  }
+
+  attr(name: string) {
+    return `data-${this.identifier}-${name}`
+  }
+
+  get element() {
+    return this.controller.element
+  }
+}