diff --git a/core/src/list.c b/core/src/list.c
index 3035375..1f92ba1 100644
--- a/core/src/list.c
+++ b/core/src/list.c
@@ -89,7 +89,7 @@ size_t list_add(List* self, void* item) {
         .as_void = self->data
     };
 
-    uint8_t* into = data.as_byte + self->element_size * self->len;
+    uint8_t* into = data.as_byte + (self->element_size * self->len);
 
     memcpy(into, item, self->element_size);
     ++self->len;
@@ -100,7 +100,7 @@ size_t list_add(List* self, void* item) {
 void list_insert(List* self, void* item, size_t at) {
     list_reserve(self, self->len + 1);
 
-    if(at == self->len - 1) {
+    if(at >= self->len) {
         list_add(self, item);
         return;
     }
@@ -111,9 +111,9 @@ void list_insert(List* self, void* item, size_t at) {
     } data = {
         .as_void = self->data
     };
-    uint8_t* from = data.as_byte + self->element_size * at;
-    uint8_t* into = data.as_byte + self->element_size * (at + 1);
-    uint8_t* end = data.as_byte + self->element_size * self->len;
+    uint8_t* from = data.as_byte + (self->element_size * at);
+    uint8_t* into = data.as_byte + (self->element_size * (at + 1));
+    uint8_t* end = data.as_byte + (self->element_size * self->len);
     memmove(into, from, end - from);
     memcpy(from, item, self->element_size);
     ++self->len;