diff --git a/src/lib.rs b/src/lib.rs
index d81c1d16..f8bb4125 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -159,8 +159,11 @@ pub fn optimize(filepath: &Path, opts: &Options) -> Result<(), String> {
 
         for result in results {
             if let Ok(ok_result) = result.join() {
-                if ok_result.4.len() < png.idat_data.len() ||
-                    (best.is_none() && something_changed) {
+                if (best.is_some() && ok_result.4.len() < best.clone().unwrap().4.len()) ||
+                   (best.is_none() &&
+                    (ok_result.4.len() < png.idat_data.len() ||
+                     opts.interlace != Some(png.ihdr_data.interlaced) ||
+                     opts.force)) {
                     best = Some(ok_result);
                 }
             }
@@ -242,12 +245,14 @@ pub fn optimize(filepath: &Path, opts: &Options) -> Result<(), String> {
         println!("    file size = {} bytes ({} bytes = {:.2}% decrease)",
                  output_data.len(),
                  file_original_size - output_data.len(),
-                 (file_original_size - output_data.len()) as f64 / file_original_size as f64 * 100f64);
+                 (file_original_size - output_data.len()) as f64 / file_original_size as f64 *
+                 100f64);
     } else {
         println!("    file size = {} bytes ({} bytes = {:.2}% increase)",
                  output_data.len(),
                  output_data.len() - file_original_size,
-                 (output_data.len() - file_original_size) as f64 / file_original_size as f64 * 100f64);
+                 (output_data.len() - file_original_size) as f64 / file_original_size as f64 *
+                 100f64);
     }
 
     Ok(())
diff --git a/src/png.rs b/src/png.rs
index 2aace7fb..f1173e90 100644
--- a/src/png.rs
+++ b/src/png.rs
@@ -263,7 +263,9 @@ impl PngData {
         output.append(&mut ihdr_data);
         output.write_u32::<BigEndian>(crc).ok();
         // Ancillary headers
-        for (key, header) in self.aux_headers.iter().filter(|&(ref key, _)| !(**key == "bKGD" || **key == "hIST" || **key == "tRNS")) {
+        for (key, header) in self.aux_headers.iter().filter(|&(ref key, _)| {
+            !(**key == "bKGD" || **key == "hIST" || **key == "tRNS")
+        }) {
             let mut header_data = Vec::with_capacity(header.len() + 4);
             header_data.extend(key.as_bytes());
             header_data.extend_from_slice(header);
@@ -306,7 +308,9 @@ impl PngData {
             output.write_u32::<BigEndian>(crc).ok();
         }
         // Special ancillary headers that need to come after PLTE but before IDAT
-        for (key, header) in self.aux_headers.iter().filter(|&(ref key, _)| **key == "bKGD" || **key == "hIST" || **key == "tRNS") {
+        for (key, header) in self.aux_headers.iter().filter(|&(ref key, _)| {
+            **key == "bKGD" || **key == "hIST" || **key == "tRNS"
+        }) {
             let mut header_data = Vec::with_capacity(header.len() + 4);
             header_data.extend(key.as_bytes());
             header_data.extend_from_slice(header);
diff --git a/tests/oxipng.rs b/tests/oxipng.rs
index 0e6118a7..dbc4d08a 100644
--- a/tests/oxipng.rs
+++ b/tests/oxipng.rs
@@ -12,7 +12,6 @@ use std::path::PathBuf;
 fn get_opts(input: &Path) -> oxipng::Options {
     let mut filter = HashSet::new();
     filter.insert(0);
-    filter.insert(5);
     let mut compression = HashSet::new();
     compression.insert(9);
     let mut memory = HashSet::new();