diff --git a/README.md b/README.md
index 8eecd1b..c54fb74 100644
--- a/README.md
+++ b/README.md
@@ -8,7 +8,9 @@ Patches may outdate, so open an issue
 if you get an error while script applies them.
 
 ## How to build
-1. Install dependencies: `doas apk add git openjdk17 7zip`
+1. Install dependencies: `doas apk add git openjdk17 openjdk21 7zip`
+(Note that both OpenJDK 17 and 21 are installed,
+for building reqwest4j and Piped respectively)
 2. Install Rust: `curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh`  
 (Note that you don't need doas or sudo here)
 3. Enter to RustUp environment: `source ~/.cargo/env`
diff --git a/build.sh b/build.sh
index addd112..12d2733 100755
--- a/build.sh
+++ b/build.sh
@@ -68,8 +68,13 @@ cd_and_exec reqwest4j/reqwest-jni \
     cargo build --release --target x86_64-unknown-linux-musl
 
 title 'Building reqwest4j without Rust library...'
+OLD_PATH="$PATH"
+export JAVA_HOME="/usr/lib/jvm/java-17-openjdk"
+export PATH="$JAVA_HOME/bin:$PATH"
 cd_and_exec reqwest4j ./gradlew shadowJar
 cd_and_exec reqwest4j ./gradlew --stop
+export PATH="$OLD_PATH"
+unset JAVA_HOME
 
 
 # ---
@@ -120,8 +125,13 @@ title 'Creating VERSION file...'
 cd_and_exec backend set_piped_version
 
 title 'Building Piped...'
+OLD_PATH="$PATH"
+export JAVA_HOME="/usr/lib/jvm/java-21-openjdk"
+export PATH="$JAVA_HOME/bin:$PATH"
 cd_and_exec backend ./gradlew shadowJar
 cd_and_exec backend ./gradlew --stop
+export PATH="$OLD_PATH"
+unset JAVA_HOME
 
 
 # ---