diff --git a/.github/workflows/draftrelease.yml b/.github/workflows/draftrelease.yml
index b906a9f..9103715 100644
--- a/.github/workflows/draftrelease.yml
+++ b/.github/workflows/draftrelease.yml
@@ -59,7 +59,7 @@ jobs:
       - name: Run ECT (-9999) on built .jar files
         run: for file in ./build/libs/*.jar; do ./ci-tools/ect-ubuntu-x86-64 -9999 --disable-png --disable-jpg -strip -zip $file; done
       - name: Run JarTighten on built .jar files
-        run: for file in ./build/libs/*.jar; do java -jar ./ci-tools/JarTighten-1.2.6-all.jar -o -c -E -S -t -z -j --mode=EXTENSIVE --zopfli-iter=9999 --optimise-existing-streams --optimise-recompressed-streams --compare-size-bits $file $file; done
+        run: for file in ./build/libs/*.jar; do java -jar ./ci-tools/JarTighten-1.2.12-all.jar -o -c -E -S -t -z -j --mode=EXTENSIVE --zopfli-iter=999 --optimise-existing-streams --optimise-recompressed-streams --merge-blocks --compare-size-bits $file $file; done
       - name: Draft release
         uses: softprops/action-gh-release@v1
         with:
diff --git a/.github/workflows/gradle.yml b/.github/workflows/gradle.yml
index c8d7a53..3a825a9 100644
--- a/.github/workflows/gradle.yml
+++ b/.github/workflows/gradle.yml
@@ -55,7 +55,7 @@ jobs:
       - name: Run ECT (-90032) on built .jar files
         run: for file in ./build/libs/*.jar; do ./ci-tools/ect-ubuntu-x86-64 -90032 --disable-png --disable-jpg -strip -zip $file; done
       - name: Run JarTighten on built .jar files
-        run: for file in ./build/libs/*.jar; do java -jar ./ci-tools/JarTighten-1.2.6-all.jar -o -c -E -S -t -z -j --mode=MULTI_CHEAP --zopfli-iter=99 $file $file; done
+        run: for file in ./build/libs/*.jar; do java -jar ./ci-tools/JarTighten-1.2.12-all.jar -o -c -E -S -t -z -j --mode=MULTI_CHEAP --zopfli-iter=99 $file $file; done
       - name: Upload artifacts
         uses: actions/upload-artifact@v3
         with:
diff --git a/ci-tools/JarTighten-1.2.12-all.jar b/ci-tools/JarTighten-1.2.12-all.jar
new file mode 100644
index 0000000..3cba2b4
Binary files /dev/null and b/ci-tools/JarTighten-1.2.12-all.jar differ
diff --git a/ci-tools/JarTighten-1.2.6-all.jar b/ci-tools/JarTighten-1.2.6-all.jar
deleted file mode 100644
index 9d15779..0000000
Binary files a/ci-tools/JarTighten-1.2.6-all.jar and /dev/null differ