diff --git a/src/ptk_list.h b/src/ptk_list.h
index d173c2f..6fa8910 100644
--- a/src/ptk_list.h
+++ b/src/ptk_list.h
@@ -23,11 +23,15 @@
 
 #define PTK_LIST_REMOVE_AT(T, list, index) _remove_at_PtkList((void *)list.data, &list.size, index, sizeof(T))
 
-#define PTK_LIST_SET(T, list, index, elem) do {\
-    while (list.allocated <= index) {\
+#define PTK_LIST_GROW(T, list, new_size) do {\
+    while (list.allocated < new_size) {\
         /* let's hope this doesn't fail !!! */\
         _grow_PtkList((void *)&list.data, &list.allocated, sizeof(T));\
     }\
+} while (0)
+
+#define PTK_LIST_SET(T, list, index, elem) do {\
+    PTK_LIST_GROW(T, list, index + 1);\
     list.data[index] = elem;\
 } while (0)