diff --git a/src/octet/spec.cljc b/src/octet/spec.cljc
index 0fe2802..482027a 100644
--- a/src/octet/spec.cljc
+++ b/src/octet/spec.cljc
@@ -119,9 +119,9 @@
   (size* [_ data]
     (reduce (fn [acc [index data]]
               (let [type (nth types index)]
-                (if (satisfies? ISpecSize type)
-                  (+ acc (size type))
-                  (+ acc (size* type data)))))
+                (if (satisfies? ISpecDynamicSize type)
+                  (+ acc (size* type data))
+                  (+ acc (size type)))))
             0
             (map-indexed vector data)))
 
diff --git a/test/octet/tests/core.cljc b/test/octet/tests/core.cljc
index c561a71..a4f2803 100644
--- a/test/octet/tests/core.cljc
+++ b/test/octet/tests/core.cljc
@@ -196,6 +196,11 @@
       (t/is (= readed 4))
       (t/is (= data [1000])))))
 
+(t/deftest mult-indexed-specs-with-dynamic
+  (let [spec (buf/spec (buf/spec (buf/vector* buf/byte)))
+        result (buf/into spec [[[123]]])]
+    (t/is (= (buf/get-capacity result) 5))))
+
 #?(:clj
    (t/deftest spec-data-types
      (let [data [(buf/string 5) "12345"
@@ -487,4 +492,3 @@
      (if (t/successful? m)
        (set! (.-exitCode js/process) 0)
        (set! (.-exitCode js/process) 1))))
-