diff --git a/kittens/transfer/librsync.py b/kittens/transfer/librsync.py
index 60226188b..57fddca20 100644
--- a/kittens/transfer/librsync.py
+++ b/kittens/transfer/librsync.py
@@ -16,6 +16,8 @@ if TYPE_CHECKING:
 
 class StreamingJob:
 
+    expected_input_size = IO_BUFFER_SIZE
+
     def __init__(self, job: 'JobCapsule', output_buf_size: int = IO_BUFFER_SIZE):
         self.job = job
         self.finished = False
@@ -49,9 +51,9 @@ class StreamingJob:
         pass
 
 
-def drive_job_on_file(f: IO[bytes], job: 'JobCapsule') -> Iterator[memoryview]:
-    sj = StreamingJob(job)
-    input_buf = bytearray(IO_BUFFER_SIZE)
+def drive_job_on_file(f: IO[bytes], job: 'JobCapsule', input_buf_size: int = IO_BUFFER_SIZE, output_buf_size: int = IO_BUFFER_SIZE) -> Iterator[memoryview]:
+    sj = StreamingJob(job, output_buf_size=output_buf_size)
+    input_buf = bytearray(input_buf_size)
     while not sj.finished:
         sz = f.readinto(input_buf)  # type: ignore
         yield sj(memoryview(input_buf)[:sz])
@@ -61,13 +63,18 @@ def signature_of_file(path: str) -> Iterator[memoryview]:
     with open(path, 'rb') as f:
         f.seek(0, os.SEEK_END)
         fsz = f.tell()
-        job = begin_create_signature(fsz)
+        job, block_len, strong_len = begin_create_signature(fsz)
+        strong_len = max(0, strong_len)
         f.seek(0)
-        yield from drive_job_on_file(f, job)
+        # see whole.c in librsync source for size calculations
+        yield from drive_job_on_file(f, job, input_buf_size=4 * block_len, output_buf_size=12 + 4 * (4 + (strong_len or IO_BUFFER_SIZE)))
 
 
 class LoadSignature(StreamingJob):
 
+    # see whole.c in librsync source for size calculations
+    expected_input_size = 16 * 1024
+
     def __init__(self) -> None:
         job, self.signature = begin_load_signature()
         super().__init__(job, output_buf_size=0)
@@ -79,15 +86,19 @@ class LoadSignature(StreamingJob):
 def delta_for_file(path: str, sig: 'SignatureCapsule') -> Iterator[memoryview]:
     job = begin_create_delta(sig)
     with open(path, 'rb') as f:
-        yield from drive_job_on_file(f, job)
+        # see whole.c in librsync source for size calculations
+        yield from drive_job_on_file(f, job, input_buf_size=8 * IO_BUFFER_SIZE, output_buf_size=4 * IO_BUFFER_SIZE)
 
 
 class PatchFile(StreamingJob):
 
+    # see whole.c in librsync source for size calculations
+    expected_input_size = IO_BUFFER_SIZE
+
     def __init__(self, src_path: str):
         self.src_file = open(src_path, 'rb')
         job = begin_patch(self.read_from_src)
-        super().__init__(job)
+        super().__init__(job, output_buf_size=4 * IO_BUFFER_SIZE)
 
     def read_from_src(self, b: memoryview, pos: int) -> int:
         self.src_file.seek(pos)
diff --git a/kittens/transfer/rsync.c b/kittens/transfer/rsync.c
index fdf717930..0e1691bb4 100644
--- a/kittens/transfer/rsync.c
+++ b/kittens/transfer/rsync.c
@@ -64,7 +64,7 @@ begin_create_signature(PyObject *self UNUSED, PyObject *args) {
     }
 #endif
     CREATE_JOB(rs_sig_begin, NULL, block_len, strong_len, magic_number);
-    return job_capsule;
+    return Py_BuildValue("Nnn", job_capsule, (Py_ssize_t)block_len, (Py_ssize_t)strong_len);
 }
 
 #define GET_JOB_FROM_CAPSULE \
diff --git a/kittens/transfer/rsync.pyi b/kittens/transfer/rsync.pyi
index 09be9b19b..a31915082 100644
--- a/kittens/transfer/rsync.pyi
+++ b/kittens/transfer/rsync.pyi
@@ -15,7 +15,7 @@ class RsyncError(Exception):
     pass
 
 
-def begin_create_signature(file_size: int = -1, strong_len: int = 0) -> JobCapsule:
+def begin_create_signature(file_size: int = -1, strong_len: int = 0) -> Tuple[JobCapsule, int, int]:
     pass