diff --git a/kernel-shared/extent_io.c b/kernel-shared/extent_io.c
index 6dbc95ad..016aa698 100644
--- a/kernel-shared/extent_io.c
+++ b/kernel-shared/extent_io.c
@@ -1067,10 +1067,10 @@ void read_extent_buffer(const struct extent_buffer *eb, void *dst,
 	memcpy(dst, eb->data + start, len);
 }
 
-void write_extent_buffer(struct extent_buffer *eb, const void *src,
+void write_extent_buffer(const struct extent_buffer *eb, const void *src,
 			 unsigned long start, unsigned long len)
 {
-	memcpy(eb->data + start, src, len);
+	memcpy((void *)eb->data + start, src, len);
 }
 
 void copy_extent_buffer(struct extent_buffer *dst, struct extent_buffer *src,
diff --git a/kernel-shared/extent_io.h b/kernel-shared/extent_io.h
index 88fb6171..d824d467 100644
--- a/kernel-shared/extent_io.h
+++ b/kernel-shared/extent_io.h
@@ -145,7 +145,7 @@ int memcmp_extent_buffer(const struct extent_buffer *eb, const void *ptrv,
 			 unsigned long start, unsigned long len);
 void read_extent_buffer(const struct extent_buffer *eb, void *dst,
 			unsigned long start, unsigned long len);
-void write_extent_buffer(struct extent_buffer *eb, const void *src,
+void write_extent_buffer(const struct extent_buffer *eb, const void *src,
 			 unsigned long start, unsigned long len);
 void copy_extent_buffer(struct extent_buffer *dst, struct extent_buffer *src,
 			unsigned long dst_offset, unsigned long src_offset,