diff --git a/Dockerfile b/Dockerfile
index 8aeca24..60665ce 100755
--- a/Dockerfile
+++ b/Dockerfile
@@ -10,6 +10,12 @@ RUN install-php-extensions iconv gd pdo pdo_mysql pdo_pgsql pgsql \
     && apt-get clean \
     && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*
 
+COPY docker/librespeed-php.ini /tmp/librespeed-php.ini
+RUN scan_dir="$(php -r 'echo rtrim(PHP_CONFIG_FILE_SCAN_DIR);')" \
+    && [ -n "$scan_dir" ] \
+    && install -D -m 0644 /tmp/librespeed-php.ini "$scan_dir/99-librespeed.ini" \
+    && rm /tmp/librespeed-php.ini
+
 # Prepare files and folders
 RUN mkdir -p /speedtest/
 
diff --git a/Dockerfile.alpine b/Dockerfile.alpine
index 47f694b..beec4c9 100755
--- a/Dockerfile.alpine
+++ b/Dockerfile.alpine
@@ -20,6 +20,12 @@ RUN apk add --quiet --no-cache \
 RUN ln -sf /dev/stdout /var/log/apache2/access.log && \
     ln -sf /dev/stderr /var/log/apache2/error.log
 
+COPY docker/librespeed-php.ini /tmp/librespeed-php.ini
+RUN scan_dir="$(/usr/bin/php -r 'echo rtrim(PHP_CONFIG_FILE_SCAN_DIR);')" \
+    && [ -n "$scan_dir" ] \
+    && install -D -m 0644 /tmp/librespeed-php.ini "$scan_dir/99-librespeed.ini" \
+    && rm /tmp/librespeed-php.ini
+
 # Prepare files and folders
 RUN mkdir -p /speedtest/
 
diff --git a/docker/librespeed-php.ini b/docker/librespeed-php.ini
new file mode 100644
index 0000000..82bcea3
--- /dev/null
+++ b/docker/librespeed-php.ini
@@ -0,0 +1,18 @@
+; LibreSpeed-recommended PHP override.
+;
+; speedtest_worker.js uploads in 20 MB chunks by default
+; (xhr_ul_blob_megabytes: 20). PHP's stock post_max_size = 8M rejects
+; every chunk: PHP emits a "POST Content-Length ... exceeds the
+; limit" startup warning and prevents empty.php from sending its
+; response headers (Cache-Control, Pragma, Connection, and CORS
+; under ?cors).
+;
+; The upload throughput number itself is unaffected — the worker
+; reads bytes-on-wire from xhr.upload.onprogress, not the response
+; body — but the response from empty.php is otherwise malformed.
+;
+; 32M is the next round number above the worker's 20M default; it
+; leaves headroom for operators who tune xhr_ul_blob_megabytes
+; upwards.
+
+post_max_size = 32M