diff --git a/interface/apdu/pcsc.c b/interface/apdu/pcsc.c
index 47e795d..7ddc66d 100644
--- a/interface/apdu/pcsc.c
+++ b/interface/apdu/pcsc.c
@@ -379,8 +379,9 @@ static int pcsc_list_iter(int index, const char *reader, void *userdata)
 {
     cJSON *json = userdata;
     cJSON *jreader;
+    char index_str[16];
 
-    char *index_str;
+    snprintf(index_str, sizeof(index_str), "%d", index);
 
     jreader = cJSON_CreateObject();
     if (!jreader)
@@ -388,21 +389,11 @@ static int pcsc_list_iter(int index, const char *reader, void *userdata)
         return -1;
     }
 
-    index_str = malloc(16);
-    if (!index_str)
-    {
-        return -1;
-    }
-
-    snprintf(index_str, 16, "%d", index);
-
     if (!cJSON_AddStringToObject(jreader, "env", index_str))
     {
         return -1;
     }
 
-    free(index_str);
-
     if (!cJSON_AddStringToObject(jreader, "name", reader))
     {
         return -1;