diff --git a/src/utils/roomVersion.ts b/src/utils/roomVersion.ts
index e90b0ab92b..0b03cf4532 100644
--- a/src/utils/roomVersion.ts
+++ b/src/utils/roomVersion.ts
@@ -17,24 +17,19 @@ limitations under the License.
 /**
  * Room versions strings that we know about and do not use hydra semantics.
  */
-const HYDRA_ROOM_VERSIONS = ["org.matrix.hydra.11", "12"];
+const PRE_HYDRA_ROOM_VERSIONS = ["1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11"];
 
 /**
  * Checks if the given room version is one where new "hydra" power level
  * semantics (ie. room version 12 or later) should be used
  * (see https://github.com/matrix-org/matrix-spec-proposals/pull/4289).
- * This will return `true` for versions that are known to the js-sdk and
- * use hydra: any room versions unknown to the js-sdk (experimental or
- * otherwise) will cause the function to return `false`.
+ * This will return `false` for versions that are known to the js-sdk and
+ * do not use hydra: any room versions unknown to the js-sdk (experimental or
+ * otherwise) will cause the function to return true.
  *
  * @param roomVersion - The version of the room to check.
  * @returns `true` if hydra semantics should be used for the room version, `false` otherwise.
  */
 export function shouldUseHydraForRoomVersion(roomVersion: string): boolean {
-    // Future new room versions must obviously be added to the constant above,
-    // otherwise the js-sdk will use the old, pre-hydra semantics. At some point
-    // it would make sense to assume hydra for unknown versions but this will break
-    // any rooms using unknown versions, so at hydra switch time we've agreed all
-    // Element clients will only use hydra for the two specific hydra versions.
-    return HYDRA_ROOM_VERSIONS.includes(roomVersion);
+    return !PRE_HYDRA_ROOM_VERSIONS.includes(roomVersion);
 }