diff --git a/.github/workflows/coverage.yml b/.github/workflows/coverage.yml
index 4569c7c6..81bdb400 100644
--- a/.github/workflows/coverage.yml
+++ b/.github/workflows/coverage.yml
@@ -46,16 +46,16 @@ jobs:
     - name: Add Clang/LLVM repositories
       run: |-
         wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key | sudo apt-key add -
-        sudo add-apt-repository 'deb http://apt.llvm.org/bionic/ llvm-toolchain-bionic-11 main'
+        sudo add-apt-repository 'deb http://apt.llvm.org/bionic/ llvm-toolchain-bionic-13 main'
     - name: Install build dependencies
       # NOTE: Please note the version-specific ${PATH} extension for Clang in .travis.sh
       run: |-
         sudo dpkg --add-architecture i386  # for wine32
         sudo apt-get update
         sudo apt-get install --yes --no-install-recommends -V \
-            clang-11 \
-            clang-format-11 \
-            llvm-11 \
+            clang-13 \
+            clang-format-13 \
+            llvm-13 \
             cmake \
             docbook2x \
             dos2unix \
diff --git a/.github/workflows/linux.yml b/.github/workflows/linux.yml
index ca215a52..6d02d80e 100644
--- a/.github/workflows/linux.yml
+++ b/.github/workflows/linux.yml
@@ -80,16 +80,16 @@ jobs:
     - name: Add Clang/LLVM repositories
       run: |-
         wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key | sudo apt-key add -
-        sudo add-apt-repository 'deb http://apt.llvm.org/bionic/ llvm-toolchain-bionic-11 main'
+        sudo add-apt-repository 'deb http://apt.llvm.org/bionic/ llvm-toolchain-bionic-13 main'
     - name: Install build dependencies
       # NOTE: Please note the version-specific ${PATH} extension for Clang in .travis.sh
       run: |-
         sudo dpkg --add-architecture i386  # for wine32
         sudo apt-get update
         sudo apt-get install --yes --no-install-recommends -V \
-            clang-11 \
-            clang-format-11 \
-            llvm-11 \
+            clang-13 \
+            clang-format-13 \
+            llvm-13 \
             cmake \
             docbook2x \
             dos2unix \
diff --git a/.travis.sh b/.travis.sh
index 5eadba83..85802073 100755
--- a/.travis.sh
+++ b/.travis.sh
@@ -39,7 +39,7 @@ if [[ ${TRAVIS_OS_NAME} = osx ]]; then
     export PATH="/usr/local/opt/coreutils/libexec/gnubin${PATH:+:}${PATH}"
     export PATH="/usr/local/opt/findutils/libexec/gnubin${PATH:+:}${PATH}"
 elif [[ ${TRAVIS_OS_NAME} = linux ]]; then
-    export PATH="/usr/lib/llvm-11/bin:${PATH}"
+    export PATH="/usr/lib/llvm-13/bin:${PATH}"
 fi
 
 echo "New \${PATH}:"
diff --git a/expat/Changes b/expat/Changes
index af5e3cdb..51cbaa2d 100644
--- a/expat/Changes
+++ b/expat/Changes
@@ -4,7 +4,7 @@ NOTE: We are looking for help with a few things:
 
 Release x.x.x xxx xxxxxxxx xx xxxx
         Other changes:
-            #527  Address compiler warnings
+       #527 #528  Address compiler warnings
 
 Release 2.4.2 Sun December 19 2021
         Other changes:
diff --git a/expat/xmlwf/xmlwf.c b/expat/xmlwf/xmlwf.c
index 342d6c59..29118bb6 100644
--- a/expat/xmlwf/xmlwf.c
+++ b/expat/xmlwf/xmlwf.c
@@ -1128,6 +1128,8 @@ tmain(int argc, XML_Char **argv) {
 #ifdef XML_DTD
       XML_SetBillionLaughsAttackProtectionActivationThreshold(
           parser, attackThresholdBytes);
+#else
+      (void)attackThresholdBytes; // silence -Wunused-but-set-variable
 #endif
     }