diff --git a/src/extension/deflate.rs b/src/extension/deflate.rs
index 259c9083..96c56363 100644
--- a/src/extension/deflate.rs
+++ b/src/extension/deflate.rs
@@ -31,6 +31,10 @@ const SERVER_MAX_WINDOW_BITS: &str = "server_max_window_bits";
 const CLIENT_NO_CONTEXT_TAKEOVER: &str = "client_no_context_takeover";
 const CLIENT_MAX_WINDOW_BITS: &str = "client_max_window_bits";
 
+const DEFAULT_GROWTH: usize = 4096;
+const DEFAULT_DECOMPRESS_SIZE: usize = 256 * 1024 * 1024;
+const TRAILER: [u8; 4] = [0, 0, 0xff, 0xff];
+
 /// The deflate extension type.
 ///
 #[derive(Debug)]
@@ -39,9 +43,12 @@ pub struct Deflate {
     enabled: bool,
     buffer: Vec<u8>,
     params: Vec<Param<'static>>,
+    zlib_compression_level: Compression,
     our_max_window_bits: u8,
     their_max_window_bits: u8,
     await_last_fragment: bool,
+    max_buffer_size: usize,
+    grow_buffer_size: usize,
     decoder_no_context_takeover: bool,
     decoder: Decompress,
     encoder_no_context_takeover: bool,
@@ -64,9 +71,12 @@ impl Deflate {
             enabled: false,
             buffer: Vec::new(),
             params,
+            zlib_compression_level: Compression::fast(),
             our_max_window_bits: 15,
             their_max_window_bits: 15,
             await_last_fragment: false,
+            max_buffer_size: DEFAULT_DECOMPRESS_SIZE,
+            grow_buffer_size: DEFAULT_GROWTH,
             decoder_no_context_takeover: false,
             decoder: Decompress::new(false),
             encoder_no_context_takeover: false,
@@ -149,6 +159,33 @@ impl Deflate {
         }
     }
 
+    /// Set the maximum size of the internal buffer used for decompression.
+    ///
+    /// Messages that decompress to a size larger than this will fail to decode.
+    ///
+    /// The default size is 256 MiB.
+    pub fn set_max_buffer_size(&mut self, size: usize) {
+        self.max_buffer_size = size;
+    }
+
+    /// Set the size by which the internal buffer grows when it runs out of space.
+    /// The underlying Rust implementation may grow by more than this.
+    ///
+    /// The default grow size is 4096.
+    pub fn set_grow_buffer_size(&mut self, size: usize) {
+        self.grow_buffer_size = size;
+    }
+
+    /// Set the zlib compression level to use. The range is from 0 (no compression) to 9 (best compression).
+    ///
+    /// The default is 1 (fastest compression).
+    pub fn set_compression_level(&mut self, level: u32) {
+        self.zlib_compression_level = match level {
+            0..=9 => Compression::new(level),
+            _ => panic!("invalid compression level: {}", level),
+        };
+    }
+
     fn set_their_max_window_bits(&mut self, p: &Param, expected: Option<u8>) -> Result<(), ()> {
         if let Some(Ok(v)) = p.value().map(|s| s.parse::<u8>()) {
             if v < 8 || v > 15 {
@@ -323,7 +360,7 @@ impl Extension for Deflate {
         // Restore LEN and NLEN:
         data.extend_from_slice(&[0, 0, 0xff, 0xff]); // cf. RFC 7692, 7.2.2
 
-        let buffer_block_size: usize = (2 << (self.their_max_window_bits - 3)) + data.len();
+        let buffer_block_size: usize = self.grow_buffer_size + data.len();
         self.buffer.clear();
         // Guess at an initial buffer size needed.
         self.buffer.reserve(buffer_block_size);
@@ -348,13 +385,18 @@ impl Extension for Deflate {
                 }
             }
 
+            if self.buffer.len() >= self.max_buffer_size {
+                return Err(
+                    io::Error::new(io::ErrorKind::Other, "decompressed message too large").into()
+                );
+            }
             if decoder.total_in() == t_in && decoder.total_out() == t_out {
                 return Err(io::Error::new(io::ErrorKind::Other, "decompression stalled").into());
             }
             if decoder.total_in() > t_in {
                 input = &input[(decoder.total_in() - t_in) as usize..];
             }
-            self.buffer.reserve(buffer_block_size);
+            self.buffer.reserve(self.grow_buffer_size);
         }
         log::trace!(
             "decompressed {}->{} bytes, total {}/{} ratio {:.2}",
@@ -393,7 +435,11 @@ impl Extension for Deflate {
 
         if self.encoder.is_none() {
             self.encoder = Some(
-                Compress::new_with_window_bits(Compression::fast(), false, self.our_max_window_bits)
+                Compress::new_with_window_bits(
+                    self.zlib_compression_level,
+                    false,
+                    self.our_max_window_bits
+                )
             );
         }
         let encoder = self.encoder.as_mut().unwrap();
@@ -424,11 +470,11 @@ impl Extension for Deflate {
             if encoder.total_in() > t_in {
                 input = &input[(encoder.total_in() - t_in) as usize..];
             }
-            self.buffer.reserve(4096);
+            self.buffer.reserve(self.grow_buffer_size);
         }
 
         // We need to append an empty deflate block if not there yet (RFC 7692, 7.2.1).
-        while !self.buffer.ends_with(&[0, 0, 0xff, 0xff]) {
+        while !self.buffer.ends_with(&TRAILER) {
             self.buffer.reserve(5); // Make sure there is room for the trailing end bytes.
             match encoder.compress_vec(&[], &mut self.buffer, FlushCompress::Sync)? {
                 Status::Ok => {
@@ -444,8 +490,8 @@ impl Extension for Deflate {
         }
 
         // If we still have not seen the empty deflate block appended, something is wrong.
-        if !self.buffer.ends_with(&[0, 0, 0xff, 0xff]) {
-            log::error!("missing 00 00 FF FF");
+        if !self.buffer.ends_with(&TRAILER) {
+            log::error!("missing trailer {:?}", TRAILER);
             return Err(io::Error::new(io::ErrorKind::Other, "missing 00 00 FF FF").into());
         }