diff --git a/src/parsley.cpp b/src/parsley.cpp
index 3031711..8a4a7a1 100644
--- a/src/parsley.cpp
+++ b/src/parsley.cpp
@@ -4388,7 +4388,8 @@ void APar_MergeTempFile(FILE* dest_file, FILE *src_file, uint64_t src_file_size,
 			fpos_t file_offset = {0};
 			file_offset.__pos = dest_position + file_pos;
 #else
-			off_t file_offset = dest_position + file_pos;
+			fpos_t file_offset = {0};
+			*(uint64_t*) &file_offset = dest_position + file_pos;
 #endif
 			fsetpos(dest_file, &file_offset);
 			fwrite(buffer, max_buffer, 1, dest_file);
@@ -4403,7 +4404,8 @@ void APar_MergeTempFile(FILE* dest_file, FILE *src_file, uint64_t src_file_size,
 			fpos_t file_offset = {0};
 			file_offset.__pos = dest_position + file_pos;
 #else
-			off_t file_offset = dest_position + file_pos;
+			fpos_t file_offset = {0};
+			*(uint64_t*) &file_offset = dest_position + file_pos;
 #endif
 			fsetpos(dest_file, &file_offset );
 			fwrite(buffer, src_file_size - file_pos, 1, dest_file);