diff --git a/build/Dockerfile b/build/Dockerfile
index c9d9f70c..e1e0f849 100644
--- a/build/Dockerfile
+++ b/build/Dockerfile
@@ -57,10 +57,9 @@ RUN go build -o gotenberg -ldflags "-s -w -X 'github.com/gotenberg/gotenberg/v8/
 FROM debian:13-slim AS compress-go-binaries-stage
 
 RUN \
-    echo "deb http://deb.debian.org/debian bookworm-backports main" >> /etc/apt/sources.list &&\
     apt-get update -qq &&\
     apt-get upgrade -yqq &&\
-    DEBIAN_FRONTEND=noninteractive apt-get install -y -qq --no-install-recommends -t bookworm-backports upx-ucl
+    DEBIAN_FRONTEND=noninteractive apt-get install -y -qq --no-install-recommends upx-ucl
 
 COPY --from=pdfcpu-binary-stage /home/pdfcpu /home/pdfcpu
 COPY --from=gotenberg-binary-stage /home/gotenberg /home/gotenberg
@@ -211,10 +210,11 @@ ENV LANG=C.UTF-8
 ENV LC_ALL=C.UTF-8
 
 RUN \
-    # Install LibreOffice & unoconverter.
+    # Install LibreOffice & unoconverter. \
+    echo "deb http://deb.debian.org/debian trixie-backports main" >> /etc/apt/sources.list &&\
     apt-get update -qq &&\
     apt-get upgrade -yqq &&\
-    DEBIAN_FRONTEND=noninteractive apt-get install -y -qq --no-install-recommends libreoffice &&\
+    DEBIAN_FRONTEND=noninteractive apt-get install -y -qq --no-install-recommends -t trixie-backports libreoffice &&\
     curl -Ls https://raw.githubusercontent.com/gotenberg/unoconverter/v0.1.1/unoconv -o /usr/bin/unoconverter &&\
     chmod +x /usr/bin/unoconverter &&\
     # unoconverter will look for the Python binary, which has to be at version 3.
diff --git a/test/integration/features/chromium_convert_html.feature b/test/integration/features/chromium_convert_html.feature
index 10c84903..9b6ea658 100644
--- a/test/integration/features/chromium_convert_html.feature
+++ b/test/integration/features/chromium_convert_html.feature
@@ -703,7 +703,7 @@ Feature: /forms/chromium/convert/html
     Then the response header "Content-Type" should be "application/pdf"
     Then there should be 1 PDF(s) in the response
     Then the response PDF(s) should be valid "PDF/A-1b" with a tolerance of 1 failed rule(s)
-    Then the response PDF(s) should be valid "PDF/UA-1" with a tolerance of 2 failed rule(s)
+    Then the response PDF(s) should be valid "PDF/UA-1" with a tolerance of 3 failed rule(s)
 
   Scenario: POST /forms/chromium/convert/html (Split & PDF/A-1b & PDF/UA-1)
     Given I have a default Gotenberg container
@@ -734,7 +734,7 @@ Feature: /forms/chromium/convert/html
       Page 3
       """
     Then the response PDF(s) should be valid "PDF/A-1b" with a tolerance of 1 failed rule(s)
-    Then the response PDF(s) should be valid "PDF/UA-1" with a tolerance of 2 failed rule(s)
+    Then the response PDF(s) should be valid "PDF/UA-1" with a tolerance of 3 failed rule(s)
 
   # See https://github.com/gotenberg/gotenberg/issues/1130.
   Scenario: POST /forms/chromium/convert/html (Split & PDF/A-1b & PDF/UA-1 & Output Filename)
@@ -768,7 +768,7 @@ Feature: /forms/chromium/convert/html
       Page 3
       """
     Then the response PDF(s) should be valid "PDF/A-1b" with a tolerance of 1 failed rule(s)
-    Then the response PDF(s) should be valid "PDF/UA-1" with a tolerance of 2 failed rule(s)
+    Then the response PDF(s) should be valid "PDF/UA-1" with a tolerance of 3 failed rule(s)
 
   Scenario: POST /forms/chromium/convert/html (Metadata)
     Given I have a default Gotenberg container
diff --git a/test/integration/features/chromium_convert_markdown.feature b/test/integration/features/chromium_convert_markdown.feature
index 349d52ac..dd415cae 100644
--- a/test/integration/features/chromium_convert_markdown.feature
+++ b/test/integration/features/chromium_convert_markdown.feature
@@ -819,7 +819,7 @@ Feature: /forms/chromium/convert/markdown
     Then the response header "Content-Type" should be "application/pdf"
     Then there should be 1 PDF(s) in the response
     Then the response PDF(s) should be valid "PDF/A-1b" with a tolerance of 1 failed rule(s)
-    Then the response PDF(s) should be valid "PDF/UA-1" with a tolerance of 2 failed rule(s)
+    Then the response PDF(s) should be valid "PDF/UA-1" with a tolerance of 3 failed rule(s)
 
   Scenario: POST /forms/chromium/convert/markdown (Split & PDF/A-1b & PDF/UA-1)
     Given I have a default Gotenberg container
@@ -853,7 +853,7 @@ Feature: /forms/chromium/convert/markdown
       Page 3
       """
     Then the response PDF(s) should be valid "PDF/A-1b" with a tolerance of 1 failed rule(s)
-    Then the response PDF(s) should be valid "PDF/UA-1" with a tolerance of 2 failed rule(s)
+    Then the response PDF(s) should be valid "PDF/UA-1" with a tolerance of 3 failed rule(s)
 
   # See https://github.com/gotenberg/gotenberg/issues/1130.
   Scenario: POST /forms/chromium/convert/markdown (Split & PDF/A-1b & PDF/UA-1 & Output Filename)
@@ -890,7 +890,7 @@ Feature: /forms/chromium/convert/markdown
       Page 3
       """
     Then the response PDF(s) should be valid "PDF/A-1b" with a tolerance of 1 failed rule(s)
-    Then the response PDF(s) should be valid "PDF/UA-1" with a tolerance of 2 failed rule(s)
+    Then the response PDF(s) should be valid "PDF/UA-1" with a tolerance of 3 failed rule(s)
 
   Scenario: POST /forms/chromium/convert/markdown (Metadata)
     Given I have a default Gotenberg container
diff --git a/test/integration/features/chromium_convert_url.feature b/test/integration/features/chromium_convert_url.feature
index 3d5f772d..43afb4e3 100644
--- a/test/integration/features/chromium_convert_url.feature
+++ b/test/integration/features/chromium_convert_url.feature
@@ -782,7 +782,7 @@ Feature: /forms/chromium/convert/url
     Then the response header "Content-Type" should be "application/pdf"
     Then there should be 1 PDF(s) in the response
     Then the response PDF(s) should be valid "PDF/A-1b" with a tolerance of 1 failed rule(s)
-    Then the response PDF(s) should be valid "PDF/UA-1" with a tolerance of 2 failed rule(s)
+    Then the response PDF(s) should be valid "PDF/UA-1" with a tolerance of 3 failed rule(s)
 
   Scenario: POST /forms/chromium/convert/url (Split & PDF/A-1b & PDF/UA-1)
     Given I have a default Gotenberg container
@@ -814,7 +814,7 @@ Feature: /forms/chromium/convert/url
       Page 3
       """
     Then the response PDF(s) should be valid "PDF/A-1b" with a tolerance of 1 failed rule(s)
-    Then the response PDF(s) should be valid "PDF/UA-1" with a tolerance of 2 failed rule(s)
+    Then the response PDF(s) should be valid "PDF/UA-1" with a tolerance of 3 failed rule(s)
 
   # See https://github.com/gotenberg/gotenberg/issues/1130.
   Scenario: POST /forms/chromium/convert/url (Split & PDF/A-1b & PDF/UA-1 & Output Filename)
@@ -849,7 +849,7 @@ Feature: /forms/chromium/convert/url
       Page 3
       """
     Then the response PDF(s) should be valid "PDF/A-1b" with a tolerance of 1 failed rule(s)
-    Then the response PDF(s) should be valid "PDF/UA-1" with a tolerance of 2 failed rule(s)
+    Then the response PDF(s) should be valid "PDF/UA-1" with a tolerance of 3 failed rule(s)
 
   Scenario: POST /forms/chromium/convert/url (Metadata)
     Given I have a default Gotenberg container
diff --git a/test/integration/features/libreoffice_convert.feature b/test/integration/features/libreoffice_convert.feature
index 0001369c..20c903e2 100644
--- a/test/integration/features/libreoffice_convert.feature
+++ b/test/integration/features/libreoffice_convert.feature
@@ -448,7 +448,7 @@ Feature: /forms/libreoffice/convert
     Then the response header "Content-Type" should be "application/pdf"
     Then there should be 1 PDF(s) in the response
     Then the response PDF(s) should be valid "PDF/A-1b" with a tolerance of 1 failed rule(s)
-    Then the response PDF(s) should be valid "PDF/UA-1" with a tolerance of 2 failed rule(s)
+    Then the response PDF(s) should be valid "PDF/UA-1" with a tolerance of 3 failed rule(s)
 
   Scenario: POST /forms/libreoffice/convert (Split & PDF/A-1b & PDF/UA-1)
     Given I have a default Gotenberg container
@@ -479,7 +479,7 @@ Feature: /forms/libreoffice/convert
       Page 3
       """
     Then the response PDF(s) should be valid "PDF/A-1b" with a tolerance of 1 failed rule(s)
-    Then the response PDF(s) should be valid "PDF/UA-1" with a tolerance of 2 failed rule(s)
+    Then the response PDF(s) should be valid "PDF/UA-1" with a tolerance of 3 failed rule(s)
 
   Scenario: POST /forms/libreoffice/convert (Metadata)
     Given I have a default Gotenberg container
diff --git a/test/integration/features/pdfengines_convert.feature b/test/integration/features/pdfengines_convert.feature
index 867dfcf0..5ae0fd3e 100644
--- a/test/integration/features/pdfengines_convert.feature
+++ b/test/integration/features/pdfengines_convert.feature
@@ -53,7 +53,7 @@ Feature: /forms/pdfengines/convert
     Then the response header "Content-Type" should be "application/pdf"
     Then there should be 1 PDF(s) in the response
     Then the response PDF(s) should be valid "PDF/A-1b" with a tolerance of 1 failed rule(s)
-    Then the response PDF(s) should be valid "PDF/UA-1" with a tolerance of 2 failed rule(s)
+    Then the response PDF(s) should be valid "PDF/UA-1" with a tolerance of 3 failed rule(s)
 
   Scenario: POST /forms/pdfengines/convert (Many PDFs)
     Given I have a default Gotenberg container
diff --git a/test/integration/features/pdfengines_merge.feature b/test/integration/features/pdfengines_merge.feature
index 200e5035..54005dd7 100644
--- a/test/integration/features/pdfengines_merge.feature
+++ b/test/integration/features/pdfengines_merge.feature
@@ -151,7 +151,7 @@ Feature: /forms/pdfengines/merge
       Page 2
       """
     Then the response PDF(s) should be valid "PDF/A-1b" with a tolerance of 1 failed rule(s)
-    Then the response PDF(s) should be valid "PDF/UA-1" with a tolerance of 2 failed rule(s)
+    Then the response PDF(s) should be valid "PDF/UA-1" with a tolerance of 3 failed rule(s)
 
   Scenario: POST /forms/pdfengines/merge (Metadata)
     Given I have a default Gotenberg container
diff --git a/test/integration/features/pdfengines_split.feature b/test/integration/features/pdfengines_split.feature
index 387ef4ad..3566f528 100644
--- a/test/integration/features/pdfengines_split.feature
+++ b/test/integration/features/pdfengines_split.feature
@@ -343,7 +343,7 @@ Feature: /forms/pdfengines/split
       Page 3
       """
     Then the response PDF(s) should be valid "PDF/A-1b" with a tolerance of 1 failed rule(s)
-    Then the response PDF(s) should be valid "PDF/UA-1" with a tolerance of 2 failed rule(s)
+    Then the response PDF(s) should be valid "PDF/UA-1" with a tolerance of 3 failed rule(s)
 
   Scenario: POST /forms/pdfengines/split (Metadata)
     Given I have a default Gotenberg container