diff --git a/packages/runtime/container-runtime/src/test/containerRuntime.spec.ts b/packages/runtime/container-runtime/src/test/containerRuntime.spec.ts
index 16dad4546815..db50547d96fc 100644
--- a/packages/runtime/container-runtime/src/test/containerRuntime.spec.ts
+++ b/packages/runtime/container-runtime/src/test/containerRuntime.spec.ts
@@ -5,6 +5,7 @@
 
 import { strict as assert } from "node:assert";
 
+import { UsageError } from "@fluidframework/telemetry-utils/internal";
 import {
 	stringToBuffer,
 	type ILayerCompatDetails,
@@ -3872,6 +3873,25 @@ describe("Runtime", () => {
 			it("minVersionForCollab = 1.0.0", async () => {
 				const minVersionForCollab = "1.0.0";
 				const logger = new MockLogger();
+				await assert.rejects(
+					async () => {
+						await ContainerRuntime.loadRuntime2({
+							context: getMockContext({ logger }) as IContainerContext,
+							registry: new FluidDataStoreRegistry([]),
+							existing: false,
+							runtimeOptions: {},
+							provideEntryPoint: mockProvideEntryPoint,
+							minVersionForCollab,
+						});
+					},
+					(e) =>
+						e instanceof UsageError && e.message.match(/Invalid minVersionForCollab/) !== null,
+				);
+			});
+
+			it("minVersionForCollab = 1.4.0", async () => {
+				const minVersionForCollab = "1.4.0";
+				const logger = new MockLogger();
 				await ContainerRuntime.loadRuntime2({
 					context: getMockContext({ logger }) as IContainerContext,
 					registry: new FluidDataStoreRegistry([]),
diff --git a/packages/runtime/runtime-utils/src/compatibilityBase.ts b/packages/runtime/runtime-utils/src/compatibilityBase.ts
index 301f470d3764..0cdd7cca5728 100644
--- a/packages/runtime/runtime-utils/src/compatibilityBase.ts
+++ b/packages/runtime/runtime-utils/src/compatibilityBase.ts
@@ -34,17 +34,23 @@ export const defaultMinVersionForCollab =
 	"2.0.0-defaults" as const satisfies MinimumVersionForCollab;
 
 /**
- * We don't want allow a version before the major public release of the LTS version.
- * Today we use "1.0.0", because our policy supports N/N-1 & N/N-2, which includes
- * all minor versions of N. Though LTS starts at 1.4.0, we should stay consistent
- * with our policy and allow all 1.x versions to be compatible with 2.x.
+ * The lowest supported value of {@link @fluidframework/runtime-definitions#MinimumVersionForCollab}.
+ * @remarks
+ * In each new major version, this may be bumped to indicate which version of the Fluid Framework client libraries are no longer supported for collaboration.
+ * @privateRemarks
+ * At the time this was defined (and also at the time 2.0 was released), all version of 1.x below 1.4 were no longer supported.
+ * Therefore it makes sense to not support any version below 1.4.0.
+ * Supporting 1.4 is sufficient to support all 1.x versions which were maintained at the time this constant was introduced.
+ *
+ * Future major versions will have to decide which versions of every supported major (including 1.x if still supported) they want to support.
+ * Continuing to support whatever version of 1.x is the oldest supported one at the time of the major release, would make sense for 3.0.
  *
  * @privateRemarks
  * Exported for use in tests.
  *
  * @internal
  */
-export const lowestMinVersionForCollab = "1.0.0" as const satisfies MinimumVersionForCollab;
+export const lowestMinVersionForCollab = "1.4.0" as const satisfies MinimumVersionForCollab;
 
 /**
  * String in a valid semver format specifying bottom of a minor version