diff --git a/src/lib/nbt.cpp b/src/lib/nbt.cpp
index 76aecbf..acf8ee9 100644
--- a/src/lib/nbt.cpp
+++ b/src/lib/nbt.cpp
@@ -1311,7 +1311,8 @@ namespace NBT {
                         goto returnError;
                     }
                     contents.push_back(new Tag::Int8Array("", nextArray.value));
-                    *processedDataSize += (uint64_t) nextArray.value.size();
+                    // +4 for the header of the array
+                    *processedDataSize += (uint64_t) nextArray.value.size() + 4;
                 }
                 break;
             }
@@ -1370,7 +1371,8 @@ namespace NBT {
                         goto returnError;
                     }
                     contents.push_back(new Tag::Int32Array("", nextArray.value));
-                    *processedDataSize += (uint64_t) nextArray.value.size() * 4;
+                    // +4 for the header of the array
+                    *processedDataSize += (uint64_t) nextArray.value.size() * 4 + 4;
                 }
                 break;
             }
@@ -1382,7 +1384,8 @@ namespace NBT {
                         goto returnError;
                     }
                     contents.push_back(new Tag::Int64Array("", nextArray.value));
-                    *processedDataSize += (uint64_t) nextArray.value.size() * 8;
+                    // +4 for the header of the array
+                    *processedDataSize += (uint64_t) nextArray.value.size() * 8 + 4;
                 }
                 break;
             }
@@ -1627,7 +1630,8 @@ namespace NBT {
                     if (nextArray.isError) {
                         return false;
                     }
-                    *processedDataSize += (uint64_t) nextArray.value.size();
+                    // +4 for the header of the array
+                    *processedDataSize += (uint64_t) nextArray.value.size() + 4;
                 }
                 return true;
             }
@@ -1678,7 +1682,8 @@ namespace NBT {
                     if (nextArray.isError) {
                         return false;
                     }
-                    *processedDataSize += (uint64_t) nextArray.value.size() * 4;
+                    // +4 for the header of the array
+                    *processedDataSize += (uint64_t) nextArray.value.size() * 4 + 4;
                 }
                 return true;
             }
@@ -1688,7 +1693,8 @@ namespace NBT {
                     if (nextArray.isError) {
                         return false;
                     }
-                    *processedDataSize += (uint64_t) nextArray.value.size() * 8;
+                    // +4 for the header of the array
+                    *processedDataSize += (uint64_t) nextArray.value.size() * 8 + 4;
                 }
                 return true;
             }