diff --git a/Dockerfiles/ubuntu2204 b/Dockerfiles/ubuntu2204
index 2a9d407..bbec2f0 100644
--- a/Dockerfiles/ubuntu2204
+++ b/Dockerfiles/ubuntu2204
@@ -58,6 +58,7 @@ RUN export DEBIAN_FRONTEND=noninteractive && \
         asciidoctor-lists \
         asciidoctor-mathematical \
         asciidoctor-pdf \
+        asciidoctor-epub3 \
         asciidoctor-kroki \
         citeproc-ruby \
         coderay \
diff --git a/README.md b/README.md
index f3eec11..027ff7a 100644
--- a/README.md
+++ b/README.md
@@ -51,7 +51,7 @@ To build the documentation, execute the following steps:
 
 ```bash
 # run the build within the container from within the riscv-isa-manual directory
-docker run -it -v $(pwd)/riscv-isa-manual:/build riscvintl/riscv-docs-base-container-image:latest /bin/sh -c 'cd ./build; make'
+docker run -it -v $(pwd)/riscv-isa-manual:/build riscvintl/riscv-docs-base-container-image:latest /bin/sh -c 'EXPORT LANG=C.utf8; cd ./build; make'
 ```
 
 The build artifacts will be located within the `riscv-isa-manual` in the `build` directory, for instance:
@@ -101,6 +101,8 @@ To build the documentation, execute the following steps:
 docker run -it -v $(pwd)/riscv-isa-manual:/build riscvintl/riscv-docs-base-container-image:latest /bin/bash
 
 # within the container
+# asciidoctor-epub3's dependency SASS fails to parse SCSS files due to the encoding being set to ANSI_X3.4-1968
+export LANG=C.utf8
 cd ./build
 make
 ```