diff --git a/src/filter.cpp b/src/filter.cpp
index 6d7e862..44ac5cd 100644
--- a/src/filter.cpp
+++ b/src/filter.cpp
@@ -65,4 +65,5 @@ std::expected<bool, lily_png::png_error> lily_png::filter(file_reader::buffer<un
 		index_dest += scanline_size;
 		scanlines++;
 	}
+	return true;
 }
\ No newline at end of file
diff --git a/src/filter.h b/src/filter.h
index 8fec0fb..b0e0169 100644
--- a/src/filter.h
+++ b/src/filter.h
@@ -4,7 +4,7 @@
 
 namespace lily_png
 {
-    std::expected<bool, png_error> lily_png::filter_scanline(unsigned char *scanline, unsigned char *previous_scanline, unsigned char *dest, metadata &meta, unsigned char filter_type);
+    std::expected<bool, png_error> filter_scanline(unsigned char *scanline, unsigned char *previous_scanline, unsigned char *dest, metadata &meta, unsigned char filter_type);
     std::expected<bool, png_error> filter(file_reader::buffer<unsigned char> &data, file_reader::buffer<unsigned char> &dest ,metadata &meta);
 }