diff --git a/src/app/util/attribute-storage.cpp b/src/app/util/attribute-storage.cpp
index 0d1b3827e8b365..adc728157c3a1e 100644
--- a/src/app/util/attribute-storage.cpp
+++ b/src/app/util/attribute-storage.cpp
@@ -255,7 +255,7 @@ uint16_t emberAfGetDynamicIndexFromEndpoint(EndpointId id)
     {
         if (emAfEndpoints[index].endpoint == id)
         {
-            return static_cast<uint8_t>(index - FIXED_ENDPOINT_COUNT);
+            return static_cast<uint16_t>(index - FIXED_ENDPOINT_COUNT);
         }
     }
     return kEmberInvalidEndpointIndex;
@@ -322,7 +322,7 @@ EndpointId emberAfClearDynamicEndpoint(uint16_t index)
 {
     EndpointId ep = 0;
 
-    index = static_cast<uint8_t>(index + FIXED_ENDPOINT_COUNT);
+    index = static_cast<uint16_t>(index + FIXED_ENDPOINT_COUNT);
 
     if ((index < MAX_ENDPOINT_COUNT) && (emAfEndpoints[index].endpoint != kInvalidEndpointId) &&
         (emberAfEndpointIndexIsEnabled(index)))