diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index f1a2b16ec..24469d70e 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -49,7 +49,7 @@ jobs:
       - uses: Swatinem/rust-cache@v2
       - run: cargo check --workspace --examples --tests --release
       - run: cargo clean
-  test:
+  test-ubuntu:
     runs-on: ubuntu-latest
     needs: [check]
     env:
@@ -68,6 +68,48 @@ jobs:
     - uses: Swatinem/rust-cache@v2
     - run: cargo do test --nextest
     - run: cargo clean
+  test-windows:
+    runs-on: windows-latest
+    needs: [check]
+    env:
+      ZNG_TP_LICENSES: true
+      NEXTEST_RETRIES: 3
+      CC: 'clang-cl'
+      CXX: 'clang-cl'
+    steps:
+    - uses: dtolnay/rust-toolchain@stable
+    - name: install cargo-about
+      uses: baptiste0928/cargo-install@v3
+      with:
+        crate: cargo-about
+    - name: install cargo-nextest
+      uses: taiki-e/install-action@v2
+      with:
+        tool: cargo-nextest
+    - uses: actions/checkout@v4
+    - uses: Swatinem/rust-cache@v2
+    - run: cargo do test --nextest
+    - run: cargo clean
+  test-macos:
+    runs-on: macos-latest
+    needs: [check]
+    env:
+      ZNG_TP_LICENSES: true
+      NEXTEST_RETRIES: 3
+    steps:
+    - uses: dtolnay/rust-toolchain@stable
+    - name: install cargo-about
+      uses: baptiste0928/cargo-install@v3
+      with:
+        crate: cargo-about
+    - name: install cargo-nextest
+      uses: taiki-e/install-action@v2
+      with:
+        tool: cargo-nextest
+    - uses: actions/checkout@v4
+    - uses: Swatinem/rust-cache@v2
+    - run: cargo do test --nextest
+    - run: cargo clean
   test-doc:
     runs-on: ubuntu-latest
     needs: [check]
@@ -90,6 +132,6 @@ jobs:
       - run: cargo clean
   test-all:
     runs-on: ubuntu-latest
-    needs: [check-release, doc, test, test-doc, test-macro]
+    needs: [check-release, doc, test-ubuntu, test-windows, test-macos, test-doc, test-macro]
     steps:
       - run: exit 0
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index 02d2f49db..d6a3e29a8 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -78,7 +78,7 @@ jobs:
       - run: cargo clean
         if: ${{ github.event.inputs.skip_checks != 'true' }}
   check-macos:
-    runs-on: macos-13
+    runs-on: macos-latest
     steps:
       - uses: actions/checkout@v4
         if: ${{ github.event.inputs.skip_checks != 'true' }}
@@ -225,7 +225,7 @@ jobs:
           name: prebuilt-windows
           path: crates/zng-view-prebuilt/lib/zng_view.dll
   prebuild-macos:
-    runs-on: macos-13
+    runs-on: macos-latest
     needs: [check-macos]
     env:
       ZNG_TP_LICENSES: true
@@ -392,7 +392,7 @@ jobs:
       - run: cargo clean
         if: ${{ github.event.inputs.skip_tests != 'true' }}
   test-macos:
-    runs-on: macos-13
+    runs-on: macos-latest
     needs: [prebuild-macos]
     env:
       NEXTEST_RETRIES: 3
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9fbf93c3b..067193309 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -12,6 +12,7 @@
 * Fix `Img::copy_pixels`.
 * Fix `view_process::default::run_same_process` exit in headless runs.
 * Fix `AutoGrowMode::rows` actually enabling Columns auto grow.
+* Fix "unsafe precondition(s) violated" issue ([#242](https://github.com/zng-ui/zng/issues/242)).
 
 # 0.6.1
 
diff --git a/crates/zng-ext-font/src/lib.rs b/crates/zng-ext-font/src/lib.rs
index 03f7d6d22..6be454a5d 100644
--- a/crates/zng-ext-font/src/lib.rs
+++ b/crates/zng-ext-font/src/lib.rs
@@ -1019,7 +1019,7 @@ impl FontFace {
         } else {
             ColorGlyphs::load(&font)?
         };
-        let has_ligatures = face.table_with_tag(b"GSUB").is_some();
+        let has_ligatures = font.load_font_table(GSUB).is_some();
         let lig_carets = if has_ligatures {
             LigatureCaretList::empty()
         } else {
@@ -1094,7 +1094,8 @@ impl FontFace {
         } else {
             ColorGlyphs::load(&font)?
         };
-        let has_ligatures = face.table_with_tag(b"GSUB").is_some();
+
+        let has_ligatures = font.load_font_table(GSUB).is_some();
         let lig_carets = if has_ligatures {
             LigatureCaretList::empty()
         } else {
diff --git a/crates/zng-ext-font/src/ligature_util.rs b/crates/zng-ext-font/src/ligature_util.rs
index 276e3a7a9..dae2df498 100644
--- a/crates/zng-ext-font/src/ligature_util.rs
+++ b/crates/zng-ext-font/src/ligature_util.rs
@@ -12,6 +12,7 @@ use core::cmp;
 use byteorder::{BigEndian, ReadBytesExt};
 use zng_view_api::font::GlyphIndex;
 
+pub const GSUB: u32 = u32::from_be_bytes(*b"GSUB");
 const GDEF: u32 = u32::from_be_bytes(*b"GDEF");
 
 #[derive(Clone)]