diff --git a/pom.xml b/pom.xml
index 518498b..ec3dd08 100644
--- a/pom.xml
+++ b/pom.xml
@@ -21,7 +21,11 @@
     </licenses>
 
     <properties>
-        <maven.compiler.release>21</maven.compiler.release>
+        <!-- The shipped library targets Java 8 so it can be consumed by SDKs
+             on that floor (e.g. 51Degrees pipeline-java). Test sources use
+             newer language features and are compiled at a modern release
+             below; tests are not shipped. -->
+        <maven.compiler.release>8</maven.compiler.release>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
         <junit.version>5.10.2</junit.version>
     </properties>
@@ -41,6 +45,17 @@
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-compiler-plugin</artifactId>
                 <version>3.13.0</version>
+                <executions>
+                    <!-- Main sources ship at Java 8 (see maven.compiler.release).
+                         Test sources use newer language features, so compile
+                         them at a modern release. -->
+                    <execution>
+                        <id>default-testCompile</id>
+                        <configuration>
+                            <release>17</release>
+                        </configuration>
+                    </execution>
+                </executions>
             </plugin>
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
diff --git a/src/main/java/com/swancommunity/owid/Io.java b/src/main/java/com/swancommunity/owid/Io.java
index 9d0af1d..17de59d 100644
--- a/src/main/java/com/swancommunity/owid/Io.java
+++ b/src/main/java/com/swancommunity/owid/Io.java
@@ -175,7 +175,7 @@ static void writeString(ByteArrayOutputStream buffer, String value)
                 throw new OwidException("domain '" + value + "' is not valid");
             }
         }
-        buffer.writeBytes(bytes);
+        buffer.write(bytes, 0, bytes.length);
         buffer.write(0);
     }
 
@@ -198,7 +198,7 @@ static void writeByteArray(ByteArrayOutputStream buffer, byte[] value)
                     + "' exceeds the unsigned 32 bit limit");
         }
         writeUInt32(buffer, value.length);
-        buffer.writeBytes(value);
+        buffer.write(value, 0, value.length);
     }
 
     /** Writes the fixed length signature, validating the length. */
@@ -207,7 +207,7 @@ static void writeSignature(ByteArrayOutputStream buffer, byte[] value)
         if (value.length != Owid.SIGNATURE_LENGTH) {
             throw invalidSignatureLength(value.length);
         }
-        buffer.writeBytes(value);
+        buffer.write(value, 0, value.length);
     }
 
     /** Writes the date using the encoding associated with the version. */