diff --git a/src/LibBGCode/binarize/binarize.cpp b/src/LibBGCode/binarize/binarize.cpp
index 625bae5..adf4096 100644
--- a/src/LibBGCode/binarize/binarize.cpp
+++ b/src/LibBGCode/binarize/binarize.cpp
@@ -579,7 +579,7 @@ EResult ThumbnailBlock::write(FILE& file, EChecksumType checksum_type)
         return EResult::InvalidThumbnailDataSize;
 
     // write block header
-    const BlockHeader block_header((uint16_t)EBlockType::Thumbnail, (uint16_t)ECompressionType::None, (uint32_t)data.size());
+    BlockHeader block_header((uint16_t)EBlockType::Thumbnail, (uint16_t)ECompressionType::None, (uint32_t)data.size());
     EResult res = block_header.write(file);
     if (res != EResult::Success)
         // propagate error
diff --git a/src/LibBGCode/core/core.cpp b/src/LibBGCode/core/core.cpp
index 65654f6..5194b40 100644
--- a/src/LibBGCode/core/core.cpp
+++ b/src/LibBGCode/core/core.cpp
@@ -159,7 +159,7 @@ long BlockHeader::get_position() const
     return m_position;
 }
 
-EResult BlockHeader::write(FILE& file) const
+EResult BlockHeader::write(FILE& file)
 {
     m_position = ftell(&file);
     if (!write_to_file(file, &type, sizeof(type)))
diff --git a/src/LibBGCode/core/core.hpp b/src/LibBGCode/core/core.hpp
index 107aff3..1a71fa1 100644
--- a/src/LibBGCode/core/core.hpp
+++ b/src/LibBGCode/core/core.hpp
@@ -259,14 +259,14 @@ struct BlockHeader
     // Position is set by calling write() and read() methods.
     long get_position() const;
 
-    EResult write(FILE& file) const;
+    EResult write(FILE& file);
     EResult read(FILE& file);
 
     // Returs the size of this BlockHeader, in bytes
     size_t get_size() const;
 
 private:
-    mutable long m_position{ 0 };
+    long m_position{ 0 };
 };
 
 struct ThumbnailParams