diff --git a/packages/tools/mobx.ts b/packages/tools/mobx.ts
index a24bc94..c4c2b90 100644
--- a/packages/tools/mobx.ts
+++ b/packages/tools/mobx.ts
@@ -1,6 +1,6 @@
 import type { IReactionDisposer, IReactionOptions, IReactionPublic } from 'mobx';
 import { autorun, reaction } from 'mobx';
-import { debounce } from 'radash';
+import { debounce, omit } from 'radash';
 
 export function disposableReaction<T, FireImmediately extends boolean = false>(
   mustBeDisposed: () => boolean,
@@ -14,6 +14,10 @@ export function disposableReaction<T, FireImmediately extends boolean = false>(
 ) {
   let disposer: IReactionDisposer | undefined;
 
+  if (!mustBeDisposed()) {
+    disposer = reaction(expression, effect, reactionOpts);
+  }
+
   function cleanDisposer() {
     disposer = undefined;
   }
@@ -23,7 +27,8 @@ export function disposableReaction<T, FireImmediately extends boolean = false>(
       if (disposer !== undefined) disposer();
       cleanDisposer();
     } else {
-      disposer = reaction(expression, effect, reactionOpts);
+      const opts = reactionOpts ? omit(reactionOpts, ['fireImmediately']) : undefined;
+      disposer = reaction(expression, effect, opts);
     }
   });
 }