diff --git a/include/posting.h b/include/posting.h
index 094c3853..5f8cbb98 100644
--- a/include/posting.h
+++ b/include/posting.h
@@ -18,7 +18,7 @@ struct compact_posting_list_t {
     // format: num_offsets, offset1,..,offsetn, id1 | num_offsets, offset1,..,offsetn, id2
     uint32_t id_offsets[];
 
-    static compact_posting_list_t* create(uint32_t num_ids, uint32_t* ids, const uint32_t* offset_index,
+    static compact_posting_list_t* create(uint32_t num_ids, const uint32_t* ids, const uint32_t* offset_index,
                                           uint32_t num_offsets, uint32_t* offsets);
 
     posting_list_t* to_full_posting_list();
diff --git a/src/posting.cpp b/src/posting.cpp
index ff7412f8..645ba009 100644
--- a/src/posting.cpp
+++ b/src/posting.cpp
@@ -11,7 +11,7 @@ int64_t compact_posting_list_t::upsert(const uint32_t id, const uint32_t* offset
     int64_t new_storage_needed = 0;
 
     if(length == 0 || id > last_id) {
-        new_storage_needed = num_offsets + 2;
+        new_storage_needed = sizeof(uint32_t) * (num_offsets + 2);
         if(length + new_storage_needed > capacity) {
             // enough storage should have been provided upstream
             return (length + new_storage_needed) - capacity;
@@ -34,7 +34,7 @@ int64_t compact_posting_list_t::upsert(const uint32_t id, const uint32_t* offset
             size_t existing_id = id_offsets[i + num_existing_offsets + 1];
 
             if(existing_id == id) {
-                new_storage_needed = (num_offsets - num_existing_offsets);
+                new_storage_needed = sizeof(uint32_t) * (num_offsets - num_existing_offsets);
                 if(new_storage_needed > 0) {
                     if(length + new_storage_needed > capacity) {
                         // enough storage should have been provided upstream
@@ -71,7 +71,7 @@ int64_t compact_posting_list_t::upsert(const uint32_t id, const uint32_t* offset
             }
 
             else if(existing_id > id) {
-                new_storage_needed = (num_offsets + 2);
+                new_storage_needed = sizeof(uint32_t) * (num_offsets + 2);
                 if(length + new_storage_needed > capacity) {
                     // enough storage should have been provided upstream
                     return (length + new_storage_needed) - capacity;
@@ -134,7 +134,7 @@ void compact_posting_list_t::erase(const uint32_t id) {
     ids_length--;
 }
 
-compact_posting_list_t* compact_posting_list_t::create(uint32_t num_ids, uint32_t* ids, const uint32_t* offset_index,
+compact_posting_list_t* compact_posting_list_t::create(uint32_t num_ids, const uint32_t* ids, const uint32_t* offset_index,
                                                        uint32_t num_offsets, uint32_t* offsets) {
     // format: num_offsets, offset1,..,offsetn, id1 | num_offsets, offset1,..,offsetn, id2
 
@@ -420,6 +420,10 @@ bool posting_t::block_intersect(const std::vector<void*>& raw_posting_lists, siz
 }
 
 void posting_t::destroy_list(void*& obj) {
+    if(obj == nullptr) {
+        return;
+    }
+
     if(IS_COMPACT_POSTING(obj)) {
         compact_posting_list_t* list = COMPACT_POSTING_PTR(obj);
         free(list); // assigned via malloc, so must be free()d
diff --git a/src/posting_list.cpp b/src/posting_list.cpp
index e95fd283..29d6ef73 100644
--- a/src/posting_list.cpp
+++ b/src/posting_list.cpp
@@ -5,7 +5,7 @@
 /* block_t operations */
 
 uint32_t posting_list_t::block_t::upsert(const uint32_t id, const std::vector<uint32_t>& positions) {
-    if(id <= ids.last()) {
+    if(id <= ids.last() && ids.getLength() != 0) {
         // we have to check if `id` already exists, for an opportunity to do in-place updates
         uint32_t id_index = ids.indexOf(id);
 
diff --git a/test/posting_list_test.cpp b/test/posting_list_test.cpp
index 5a646abb..04234bf2 100644
--- a/test/posting_list_test.cpp
+++ b/test/posting_list_test.cpp
@@ -1043,8 +1043,10 @@ TEST(PostingListTest, CompactPostingListContainsAtleastOne) {
     compact_posting_list_t* list1 = compact_posting_list_t::create(4, ids, offset_index, 12, offsets);
     ASSERT_TRUE(list1->contains_atleast_one(&target_ids1[0], target_ids1.size()));
     ASSERT_FALSE(list1->contains_atleast_one(&target_ids2[0], target_ids2.size()));
+    free(list1);
 
     compact_posting_list_t* list2 = static_cast<compact_posting_list_t*>(malloc(sizeof(compact_posting_list_t)));
+    list2->capacity = list2->ids_length = list2->length = 0;
     void* obj = SET_COMPACT_POSTING(list2);
     posting_t::upsert(obj, 3, {1, 5});
 
@@ -1053,6 +1055,8 @@ TEST(PostingListTest, CompactPostingListContainsAtleastOne) {
 
     ASSERT_TRUE(COMPACT_POSTING_PTR(obj)->contains_atleast_one(&target_ids3[0], target_ids3.size()));
     ASSERT_FALSE(COMPACT_POSTING_PTR(obj)->contains_atleast_one(&target_ids4[0], target_ids4.size()));
+
+    posting_t::destroy_list(obj);
 }
 
 TEST(PostingListTest, DISABLED_Benchmark) {