diff --git a/src/lgdo/compression/generic.py b/src/lgdo/compression/generic.py
index 07e038e8..82dbb81b 100644
--- a/src/lgdo/compression/generic.py
+++ b/src/lgdo/compression/generic.py
@@ -40,6 +40,7 @@ def encode(
 
 def decode(
     obj: lgdo.VectorOfEncodedVectors | lgdo.ArrayOfEncodedEqualSizedArrays,
+    out_buf: lgdo.ArrayOfEqualSizedArrays = None,
 ) -> lgdo.VectorOfVectors | lgdo.ArrayOfEqualsizedArrays:
     """Decode encoded LGDOs.
 
@@ -51,6 +52,9 @@ def decode(
     ----------
     obj
         LGDO array type.
+    out_buf
+        pre-allocated LGDO for the decoded signals. See documentation of
+        wrapped encoders for limitations.
     """
     if "codec" not in obj.attrs:
         raise RuntimeError(
@@ -61,9 +65,11 @@ def decode(
     log.debug(f"decoding {repr(obj)} with {codec}")
 
     if _is_codec(codec, radware.RadwareSigcompress):
-        return radware.decode(obj, shift=int(obj.attrs.get("codec_shift", 0)))
+        return radware.decode(
+            obj, sig_out=out_buf, shift=int(obj.attrs.get("codec_shift", 0))
+        )
     elif _is_codec(codec, varlen.ULEB128ZigZagDiff):
-        return varlen.decode(obj)
+        return varlen.decode(obj, sig_out=out_buf)
     else:
         raise ValueError(f"'{codec}' not supported")
 
diff --git a/src/lgdo/compression/radware.py b/src/lgdo/compression/radware.py
index f8235d7e..f7f9bca0 100644
--- a/src/lgdo/compression/radware.py
+++ b/src/lgdo/compression/radware.py
@@ -120,7 +120,7 @@ def encode(
         return sig_out, nbytes
 
     elif isinstance(sig_in, lgdo.VectorOfVectors):
-        if sig_out:
+        if sig_out is not None:
             log.warning(
                 "a pre-allocated VectorOfEncodedVectors was given "
                 "to hold an encoded ArrayOfEqualSizedArrays. "
@@ -143,7 +143,7 @@ def encode(
         return sig_out
 
     elif isinstance(sig_in, lgdo.ArrayOfEqualSizedArrays):
-        if sig_out:
+        if sig_out is not None:
             log.warning(
                 "a pre-allocated ArrayOfEncodedEqualSizedArrays was given "
                 "to hold an encoded ArrayOfEqualSizedArrays. "
@@ -243,7 +243,7 @@ def decode(
         return sig_out, siglen
 
     elif isinstance(sig_in, lgdo.ArrayOfEncodedEqualSizedArrays):
-        if not sig_out:
+        if sig_out is None:
             # initialize output structure with decoded_size
             sig_out = lgdo.ArrayOfEqualSizedArrays(
                 dims=(1, 1),
diff --git a/src/lgdo/compression/varlen.py b/src/lgdo/compression/varlen.py
index e3a4846e..f273e038 100644
--- a/src/lgdo/compression/varlen.py
+++ b/src/lgdo/compression/varlen.py
@@ -94,7 +94,7 @@ def encode(
         return sig_out, nbytes
 
     elif isinstance(sig_in, lgdo.VectorOfVectors):
-        if sig_out:
+        if sig_out is not None:
             log.warning(
                 "a pre-allocated VectorOfEncodedVectors was given "
                 "to hold an encoded ArrayOfEqualSizedArrays. "
@@ -208,7 +208,7 @@ def decode(
         return sig_out, siglen
 
     elif isinstance(sig_in, lgdo.ArrayOfEncodedEqualSizedArrays):
-        if not sig_out:
+        if sig_out is None:
             # initialize output structure with decoded_size
             sig_out = lgdo.ArrayOfEqualSizedArrays(
                 dims=(1, 1),
diff --git a/tests/compression/test_radware_sigcompress.py b/tests/compression/test_radware_sigcompress.py
index b466e390..ac634c36 100644
--- a/tests/compression/test_radware_sigcompress.py
+++ b/tests/compression/test_radware_sigcompress.py
@@ -107,8 +107,9 @@ def test_wrapper(wftable):
 
     enc_wfs = np.zeros(s[:-1] + (2 * s[-1],), dtype="ubyte")
     enclen = np.empty(s[0], dtype="uint32")
+    _shift = np.full(s[0], shift, dtype="int32")
 
-    _radware_sigcompress_encode(wfs, enc_wfs, shift, enclen, _mask)
+    _radware_sigcompress_encode(wfs, enc_wfs, _shift, enclen, _mask)
 
     # test if the wrapper gives the same result
     w_enc_wfs, w_enclen = encode(wfs, shift=shift)