diff --git a/libluna/include/luna/Buffer.h b/libluna/include/luna/Buffer.h
index 6d6f89c0..554de586 100644
--- a/libluna/include/luna/Buffer.h
+++ b/libluna/include/luna/Buffer.h
@@ -19,7 +19,7 @@ class Buffer
 
     Result<u8*> slice(usize offset, usize size);
 
-    Result<void> append_data(u8* data, usize size);
+    Result<void> append_data(const u8* data, usize size);
 
     u8* data()
     {
diff --git a/libluna/include/luna/Result.h b/libluna/include/luna/Result.h
index 265453bc..98765412 100644
--- a/libluna/include/luna/Result.h
+++ b/libluna/include/luna/Result.h
@@ -122,7 +122,7 @@ template <typename T> class Result
         return m_value.try_move_value(ref);
     }
 
-    bool try_move_value_or_error(T& ref, int& err) const
+    bool try_move_value_or_error(T& ref, int& err)
     {
         bool ok = m_value.try_move_value(ref);
         if (!ok) err = m_error;
diff --git a/libluna/src/Buffer.cpp b/libluna/src/Buffer.cpp
index 6c385db5..b08bf35b 100644
--- a/libluna/src/Buffer.cpp
+++ b/libluna/src/Buffer.cpp
@@ -46,7 +46,7 @@ Result<u8*> Buffer::slice(usize offset, usize size)
     return m_data + offset;
 }
 
-Result<void> Buffer::append_data(u8* data, usize size)
+Result<void> Buffer::append_data(const u8* data, usize size)
 {
     memcpy(TRY(slice_at_end(size)), data, size);