diff --git a/benches/zopfli.rs b/benches/zopfli.rs
index 8c98b350..a9b91e08 100644
--- a/benches/zopfli.rs
+++ b/benches/zopfli.rs
@@ -4,16 +4,20 @@ extern crate oxipng;
 extern crate test;
 
 use oxipng::internal_tests::*;
+use std::num::NonZeroU8;
 use std::path::PathBuf;
 use test::Bencher;
 
+// SAFETY: trivially safe. Stopgap solution until const unwrap is stabilized.
+const DEFAULT_ZOPFLI_ITERATIONS: NonZeroU8 = unsafe { NonZeroU8::new_unchecked(15) };
+
 #[bench]
 fn zopfli_16_bits_strategy_0(b: &mut Bencher) {
     let input = test::black_box(PathBuf::from("tests/files/rgb_16_should_be_rgb_16.png"));
     let png = PngData::new(&input, false).unwrap();
 
     b.iter(|| {
-        zopfli_deflate(png.raw.data.as_ref()).ok();
+        zopfli_deflate(png.raw.data.as_ref(), DEFAULT_ZOPFLI_ITERATIONS).ok();
     });
 }
 
@@ -23,7 +27,7 @@ fn zopfli_8_bits_strategy_0(b: &mut Bencher) {
     let png = PngData::new(&input, false).unwrap();
 
     b.iter(|| {
-        zopfli_deflate(png.raw.data.as_ref()).ok();
+        zopfli_deflate(png.raw.data.as_ref(), DEFAULT_ZOPFLI_ITERATIONS).ok();
     });
 }
 
@@ -35,7 +39,7 @@ fn zopfli_4_bits_strategy_0(b: &mut Bencher) {
     let png = PngData::new(&input, false).unwrap();
 
     b.iter(|| {
-        zopfli_deflate(png.raw.data.as_ref()).ok();
+        zopfli_deflate(png.raw.data.as_ref(), DEFAULT_ZOPFLI_ITERATIONS).ok();
     });
 }
 
@@ -47,7 +51,7 @@ fn zopfli_2_bits_strategy_0(b: &mut Bencher) {
     let png = PngData::new(&input, false).unwrap();
 
     b.iter(|| {
-        zopfli_deflate(png.raw.data.as_ref()).ok();
+        zopfli_deflate(png.raw.data.as_ref(), DEFAULT_ZOPFLI_ITERATIONS).ok();
     });
 }
 
@@ -59,6 +63,6 @@ fn zopfli_1_bits_strategy_0(b: &mut Bencher) {
     let png = PngData::new(&input, false).unwrap();
 
     b.iter(|| {
-        zopfli_deflate(png.raw.data.as_ref()).ok();
+        zopfli_deflate(png.raw.data.as_ref(), DEFAULT_ZOPFLI_ITERATIONS).ok();
     });
 }
diff --git a/src/deflate/mod.rs b/src/deflate/mod.rs
index 7a8af8a6..9894a5b0 100644
--- a/src/deflate/mod.rs
+++ b/src/deflate/mod.rs
@@ -4,6 +4,9 @@ use crate::Deadline;
 use crate::PngResult;
 use indexmap::IndexSet;
 
+#[cfg(feature = "zopfli")]
+use std::num::NonZeroU8;
+
 #[doc(hidden)]
 pub mod miniz_stream;
 
@@ -49,11 +52,14 @@ pub fn deflate(
 }
 
 #[cfg(feature = "zopfli")]
-pub fn zopfli_deflate(data: &[u8]) -> PngResult<Vec<u8>> {
+pub fn zopfli_deflate(data: &[u8], iterations: NonZeroU8) -> PngResult<Vec<u8>> {
     use std::cmp::max;
 
     let mut output = Vec::with_capacity(max(1024, data.len() / 20));
-    let options = zopfli::Options::default();
+    let options = zopfli::Options {
+        iteration_count: iterations,
+        ..Default::default()
+    };
     match zopfli::compress(&options, &zopfli::Format::Zlib, data, &mut output) {
         Ok(_) => (),
         Err(_) => return Err(PngError::new("Failed to compress in zopfli")),
@@ -85,7 +91,12 @@ pub enum Deflaters {
     },
     #[cfg(feature = "zopfli")]
     /// Use the better but slower Zopfli implementation
-    Zopfli,
+    Zopfli {
+        /// The number of compression iterations to do. 15 iterations are fine
+        /// for small files, but bigger files will need to be compressed with
+        /// less iterations, or else they will be too slow.
+        iterations: NonZeroU8,
+    },
     #[cfg(feature = "libdeflater")]
     /// Use libdeflater.
     Libdeflater,
diff --git a/src/lib.rs b/src/lib.rs
index 441d8849..4910e50f 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -618,7 +618,7 @@ fn optimize_png(
                     &deadline,
                 ),
                 #[cfg(feature = "zopfli")]
-                Deflaters::Zopfli => deflate::zopfli_deflate(filtered),
+                Deflaters::Zopfli { iterations } => deflate::zopfli_deflate(filtered, iterations),
                 #[cfg(feature = "libdeflater")]
                 Deflaters::Libdeflater => deflate::libdeflater_deflate(filtered, &best_size),
             };
diff --git a/src/main.rs b/src/main.rs
index 02518118..adf51a4a 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -22,6 +22,7 @@ use oxipng::Headers;
 use oxipng::Options;
 use oxipng::{InFile, OutFile};
 use std::fs::DirBuilder;
+use std::num::NonZeroU8;
 use std::path::PathBuf;
 use std::process::exit;
 use std::time::Duration;
@@ -495,7 +496,9 @@ fn parse_opts_into_struct(
     }
 
     if matches.is_present("zopfli") {
-        opts.deflate = Deflaters::Zopfli;
+        opts.deflate = Deflaters::Zopfli {
+            iterations: NonZeroU8::new(15).unwrap(),
+        };
     } else if matches.is_present("libdeflater") {
         opts.deflate = Deflaters::Libdeflater;
     } else if let Deflaters::Zlib {
diff --git a/tests/flags.rs b/tests/flags.rs
index 07f29d19..f99324bd 100644
--- a/tests/flags.rs
+++ b/tests/flags.rs
@@ -4,6 +4,7 @@ use oxipng::{InFile, OutFile};
 #[cfg(feature = "filetime")]
 use std::cell::RefCell;
 use std::fs::remove_file;
+use std::num::NonZeroU8;
 #[cfg(feature = "filetime")]
 use std::ops::Deref;
 use std::path::Path;
@@ -582,7 +583,9 @@ fn fix_errors() {
 fn zopfli_mode() {
     let input = PathBuf::from("tests/files/zopfli_mode.png");
     let (output, mut opts) = get_opts(&input);
-    opts.deflate = Deflaters::Zopfli;
+    opts.deflate = Deflaters::Zopfli {
+        iterations: NonZeroU8::new(15).unwrap(),
+    };
 
     test_it_converts(
         input,