diff --git a/src/borg/helpers/parseformat.py b/src/borg/helpers/parseformat.py
index 789232a5d7..57dad2dd2a 100644
--- a/src/borg/helpers/parseformat.py
+++ b/src/borg/helpers/parseformat.py
@@ -411,6 +411,10 @@ def ChunkerParams(s):
             raise ArgumentTypeError("max. chunk size exponent must not be more than 23 (2^23 = 8MiB max. chunk size)")
         if window_size % 2 == 0:
             raise ArgumentTypeError("window_size must be an uneven (odd) number")
+        # the chunker needs the hash window plus one byte beyond the min. chunk size to fit into
+        # a max. chunk size sized buffer, see the assertion in Chunker.__cinit__ (buzhash.pyx).
+        if window_size + 2**chunk_min + 1 > 2**chunk_max:
+            raise ArgumentTypeError("required: window_size + 2^chunk_min + 1 <= 2^chunk_max")
         return CH_BUZHASH, chunk_min, chunk_max, chunk_mask, window_size
     raise ArgumentTypeError("invalid chunker params")
 
diff --git a/src/borg/testsuite/helpers/parseformat_test.py b/src/borg/testsuite/helpers/parseformat_test.py
index c1abc6f728..0facb3e85f 100644
--- a/src/borg/testsuite/helpers/parseformat_test.py
+++ b/src/borg/testsuite/helpers/parseformat_test.py
@@ -898,6 +898,7 @@ def test_eval_escapes():
         ("19,23,21,4095", ("buzhash", 19, 23, 21, 4095)),
         ("buzhash,19,23,21,4095", ("buzhash", 19, 23, 21, 4095)),
         ("10,23,16,4095", ("buzhash", 10, 23, 16, 4095)),
+        ("10,13,11,4095", ("buzhash", 10, 13, 11, 4095)),  # just fits: 4095 + 1024 + 1 <= 8192
         ("buzhash64,19,23,21,4095,2", ("buzhash64", 19, 23, 21, 4095, 2)),
         ("fastcdc,19,23,21,2", ("fastcdc", 19, 23, 21, 2)),
         ("fixed,4096", ("fixed", 4096, 0)),
@@ -917,6 +918,8 @@ def test_valid_chunkerparams(chunker_params, expected_return):
         "buzhash,23,19,21,4095",  # violates min <= mask <= max
         "buzhash,19,23,21,4096",  # even window size
         "buzhash,19,23,21",  # missing window_size (must not fall into old-style compat mode)
+        "buzhash,10,12,11,4095",  # window_size + 2^chunk_min + 1 > 2^chunk_max
+        "19,19,19,4095",  # dito, chunk_min == chunk_max (old-style compat mode)
         "buzhash64,20,20,20,4095,2",  # window_size + 2^chunk_min + 1 > 2^chunk_max
         "buzhash64,19,19,19,4095,2",  # dito, chunk_min == chunk_max
         "buzhash64,19,23,21,4095",  # missing nc_level