diff --git a/protocol/src/main/resources/rust/byte_buffer.rs b/protocol/src/main/resources/rust/byte_buffer.rs
index d26cb40c..b8fefa9f 100644
--- a/protocol/src/main/resources/rust/byte_buffer.rs
+++ b/protocol/src/main/resources/rust/byte_buffer.rs
@@ -78,7 +78,7 @@ impl IByteBuffer for ByteBuffer {
     }
 
     fn getCapacity(&self) -> i32 {
-        return self.buffer.capacity() as i32 - self.writeOffset;
+        return self.buffer.len() as i32 - self.writeOffset;
     }
 
     fn ensureCapacity(&mut self, capacity: i32) {
diff --git a/protocol/src/test/rust/zfoorust/byte_buffer.rs b/protocol/src/test/rust/zfoorust/byte_buffer.rs
index 2c879946..23d7b740 100644
--- a/protocol/src/test/rust/zfoorust/byte_buffer.rs
+++ b/protocol/src/test/rust/zfoorust/byte_buffer.rs
@@ -78,7 +78,7 @@ impl IByteBuffer for ByteBuffer {
     }
 
     fn getCapacity(&self) -> i32 {
-        return self.buffer.capacity() as i32 - self.writeOffset;
+        return self.buffer.len() as i32 - self.writeOffset;
     }
 
     fn ensureCapacity(&mut self, capacity: i32) {