diff --git a/Dockerfile b/Dockerfile
index 77245b6..77631f1 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -9,9 +9,13 @@ FROM jlesage/baseimage-gui:alpine-3.7-v3.3.4
 
 # Define software versions.
 ARG FIREFOX_VERSION=58.0.1-r2
+ARG JSONLZ4_VERSION=c4305b8
+ARG LZ4_VERSION=1.8.1.2
 #ARG PROFILE_CLEANER_VERSION=2.36
 
 # Define software download URLs.
+ARG JSONLZ4_URL=https://github.com/avih/dejsonlz4/archive/${JSONLZ4_VERSION}.tar.gz
+ARG LZ4_URL=https://github.com/lz4/lz4/archive/v${LZ4_VERSION}.tar.gz
 #ARG PROFILE_CLEANER_URL=https://github.com/graysky2/profile-cleaner/raw/v${PROFILE_CLEANER_VERSION}/common/profile-cleaner.in
 
 # Define working directory.
@@ -40,6 +44,29 @@ RUN \
     echo 'pref("browser.download.dir", "/config/downloads");' >> "$CFG_FILE" && \
     echo 'pref("browser.download.folderList", 2);' >> "$CFG_FILE"
 
+# Install JSONLZ4 tools.
+RUN \
+    add-pkg --virtual build-dependencies \
+        curl \
+        build-base \
+        && \
+    mkdir jsonlz4 && \
+    mkdir lz4 && \
+    curl -# -L {$JSONLZ4_URL} | tar xz --strip 1 -C jsonlz4 && \
+    curl -# -L {$LZ4_URL} | tar xz --strip 1 -C lz4 && \
+    mv jsonlz4/src/ref_compress/*.c jsonlz4/src/ && \
+    cp lz4/lib/lz4.* jsonlz4/src/ && \
+    cd jsonlz4 && \
+    gcc -Wall -o dejsonlz4 src/dejsonlz4.c src/lz4.c && \
+    gcc -Wall -o jsonlz4 src/jsonlz4.c src/lz4.c && \
+    strip dejsonlz4 jsonlz4 && \
+    cp -v dejsonlz4 /usr/bin/ && \
+    cp -v jsonlz4 /usr/bin/ && \
+    cd .. && \
+    # Cleanup.
+    del-pkg build-dependencies && \
+    rm -rf /tmp/* /tmp/.[!.]*
+
 # Install profile-cleaner.
 #RUN \
 #    add-pkg --virtual build-dependencies curl && \
diff --git a/rootfs/etc/cont-init.d/firefox.sh b/rootfs/etc/cont-init.d/firefox.sh
index 64e68eb..94d7402 100755
--- a/rootfs/etc/cont-init.d/firefox.sh
+++ b/rootfs/etc/cont-init.d/firefox.sh
@@ -29,6 +29,29 @@ fi
 #    env HOME=/config /usr/bin/profile-cleaner f
 #fi
 
+# Fix window display size is session stores.
+if [ -n "$(ls /config/profile/sessionstore-backups/*.jsonlz4 2>/dev/null)" ]; then
+    for FILE in /config/profile/sessionstore-backups/*.jsonlz4; do
+        WORKDIR="$(mktemp -d)"
+
+        dejsonlz4 "$FILE" "$WORKDIR"/json
+        cp "$WORKDIR"/json "$WORKDIR"/json.orig
+
+        sed -i 's/"width":[0-9]\+/"width":'$DISPLAY_WIDTH'/' "$WORKDIR"/json
+        sed -i 's/"height":[0-9]\+/"height":'$DISPLAY_HEIGHT'/' "$WORKDIR"/json
+        sed -i 's/"screenX":[0-9]\+/"screenX":0/' "$WORKDIR"/json
+        sed -i 's/"screenY":[0-9]\+/"screenY":0/' "$WORKDIR"/json
+
+        if ! diff "$WORKDIR"/json "$WORKDIR"/json.orig >/dev/null; then
+            jsonlz4 "$WORKDIR"/json "$WORKDIR"/jsonlz4
+            mv "$WORKDIR"/jsonlz4 "$FILE"
+            log "fixed display size in $FILE."
+        fi
+
+        rm -r "$WORKDIR"
+    done
+fi
+
 # Make sure monitored log files exist.
 for LOG_FILE in /config/log/firefox/error.log
 do