diff --git a/Cargo.lock b/Cargo.lock
index 6cd7ecf1b..4489cddd5 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1128,7 +1128,7 @@ dependencies = [
  "craft-drawingml",
  "craft-math",
  "craft-offcrypto",
- "craft-opc",
+ "craft-opc 0.1.0 (git+https://github.com/storytold/craft-libs?rev=ba24fe2435adb3c81ad6057faf36365fbba736cf)",
  "craft-wordmodel",
  "craft-xml 0.1.0 (git+https://github.com/storytold/craft-libs?rev=ba24fe2435adb3c81ad6057faf36365fbba736cf)",
  "log",
@@ -1306,6 +1306,17 @@ dependencies = [
  "zeroize",
 ]
 
+[[package]]
+name = "craft-opc"
+version = "0.1.0"
+source = "git+https://github.com/storytold/craft-libs?rev=8abfa9d0f14bafbfc3449fc552ffeafb9ca6a551#8abfa9d0f14bafbfc3449fc552ffeafb9ca6a551"
+dependencies = [
+ "craft-xml 0.1.0 (git+https://github.com/storytold/craft-libs?rev=8abfa9d0f14bafbfc3449fc552ffeafb9ca6a551)",
+ "craft-zip 0.1.0 (git+https://github.com/storytold/craft-libs?rev=8abfa9d0f14bafbfc3449fc552ffeafb9ca6a551)",
+ "log",
+ "thiserror 2.0.21",
+]
+
 [[package]]
 name = "craft-opc"
 version = "0.1.0"
@@ -1492,7 +1503,7 @@ version = "0.1.0"
 source = "git+https://github.com/storytold/craft-libs?rev=ba24fe2435adb3c81ad6057faf36365fbba736cf#ba24fe2435adb3c81ad6057faf36365fbba736cf"
 dependencies = [
  "craft-drawingml",
- "craft-opc",
+ "craft-opc 0.1.0 (git+https://github.com/storytold/craft-libs?rev=ba24fe2435adb3c81ad6057faf36365fbba736cf)",
  "craft-sheet",
  "craft-xml 0.1.0 (git+https://github.com/storytold/craft-libs?rev=ba24fe2435adb3c81ad6057faf36365fbba736cf)",
  "thiserror 2.0.21",
@@ -1938,6 +1949,7 @@ name = "designcraft-pptx"
 version = "0.20.1"
 dependencies = [
  "chrono",
+ "craft-opc 0.1.0 (git+https://github.com/storytold/craft-libs?rev=8abfa9d0f14bafbfc3449fc552ffeafb9ca6a551)",
  "designcraft-color",
  "designcraft-compose",
  "designcraft-doc",
diff --git a/Cargo.toml b/Cargo.toml
index ca146fb5e..9dbba9581 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -28,6 +28,7 @@ craft-csv = { git = "https://github.com/storytold/craft-libs", rev = "47bf5650b0
 craft-image-codecs = { git = "https://github.com/storytold/craft-libs", rev = "a47b78256c6acf3d7fdc4bc7cfbc25c373eac522", version = "=0.1.0" }
 craft-psd = { git = "https://github.com/storytold/craft-libs", rev = "a47b78256c6acf3d7fdc4bc7cfbc25c373eac522", version = "=0.1.0" }
 craft-file-formats = { git = "https://github.com/storytold/craft-libs", rev = "8abfa9d0f14bafbfc3449fc552ffeafb9ca6a551", version = "=0.1.0" }
+craft-opc = { git = "https://github.com/storytold/craft-libs", rev = "8abfa9d0f14bafbfc3449fc552ffeafb9ca6a551", version = "=0.1.0" }
 # Shared keyboard bindings: chords, overrides, conflicts, egui dispatch, the Keyboard Shortcuts dialog.
 craft-keymap = { git = "https://github.com/storytold/craft-libs", rev = "92d392cff132eaf53e13afff77f38b5c11b73aa0", version = "=0.1.0", features = ["egui", "ui"] }
 # Separations, ink coverage and the ink manager; same revision as craft-pdf and the krilla patch.
diff --git a/crates/pptx/Cargo.toml b/crates/pptx/Cargo.toml
index afc90c69c..c81e72d48 100644
--- a/crates/pptx/Cargo.toml
+++ b/crates/pptx/Cargo.toml
@@ -18,9 +18,10 @@ designcraft-images = { workspace = true }
 skrifa = { workspace = true }
 image = { workspace = true }
 thiserror = { workspace = true }
-zip = { workspace = true }
+craft-opc = { workspace = true }
 chrono = { workspace = true }
 
 [dev-dependencies]
+zip = { workspace = true }
 designcraft-fonts = { workspace = true, features = ["testing"] }
 quick-xml = { workspace = true }
diff --git a/crates/pptx/src/package.rs b/crates/pptx/src/package.rs
index 7e9e123e0..5ff1fa160 100644
--- a/crates/pptx/src/package.rs
+++ b/crates/pptx/src/package.rs
@@ -1,11 +1,9 @@
 //! The PresentationML package: one blank master and layout, a theme, the slides and their media.
 
-use std::fmt::Write as _;
-use std::io::Write as _;
-
 use crate::fonts::EmbeddedFont;
 use crate::xml::{emu_len, esc};
 use crate::{PptxError, Result};
+use std::fmt::Write as _;
 
 pub const NS: &str = r#"xmlns:a="http://schemas.openxmlformats.org/drawingml/2006/main" xmlns:r="http://schemas.openxmlformats.org/officeDocument/2006/relationships" xmlns:p="http://schemas.openxmlformats.org/presentationml/2006/main""#;
 const DECL: &str = "<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"yes\"?>\n";
@@ -241,26 +239,10 @@ pub fn write(p: &Package) -> Result<Vec<u8>> {
         ),
     );
 
-    let mut zw = zip::ZipWriter::new(std::io::Cursor::new(Vec::new()));
-    let deflate = zip::write::SimpleFileOptions::default().compression_method(zip::CompressionMethod::Deflated);
-    let stored = zip::write::SimpleFileOptions::default().compression_method(zip::CompressionMethod::Stored);
-    let zerr = |e: zip::result::ZipError| PptxError::Write(e.to_string());
-    let ioerr = |e: std::io::Error| PptxError::Write(e.to_string());
-    for (name, bytes) in &parts {
-        zw.start_file(name.as_str(), deflate).map_err(zerr)?;
-        zw.write_all(bytes).map_err(ioerr)?;
-    }
-    for (name, bytes) in &font_parts {
-        zw.start_file(name.as_str(), deflate).map_err(zerr)?;
-        zw.write_all(bytes).map_err(ioerr)?;
-    }
-    for m in p.media {
-        // Compressed formats gain nothing from deflate.
-        let opts = if m.name.ends_with(".svg") { deflate } else { stored };
-        zw.start_file(format!("ppt/media/{}", m.name), opts).map_err(zerr)?;
-        zw.write_all(&m.bytes).map_err(ioerr)?;
-    }
-    Ok(zw.finish().map_err(zerr)?.into_inner())
+    let mut entries = parts;
+    entries.extend(font_parts.into_iter().map(|(name, bytes)| (name, bytes.to_vec())));
+    entries.extend(p.media.iter().map(|m| (format!("ppt/media/{}", m.name), m.bytes.clone())));
+    craft_opc::zip_entries(&entries).map_err(|e| PptxError::Write(e.to_string()))
 }
 
 fn rel_kind(k: &str) -> &'static str {