diff --git a/src/gambit/kmers.py b/src/gambit/kmers.py
index 26e150f..34ccb6c 100644
--- a/src/gambit/kmers.py
+++ b/src/gambit/kmers.py
@@ -129,7 +129,7 @@ def __from_json__(cls, data: dict[str, Any]) -> 'KmerSpec':
 
 @attrs(slots=True)
 class KmerMatch:
-	"""Represents a
+	"""Represents the location of a k-mer prefix found within a DNA sequence.
 
 	Attributes
 	----------
diff --git a/src/gambit/metric.py b/src/gambit/metric.py
index cc23e34..2b0f292 100644
--- a/src/gambit/metric.py
+++ b/src/gambit/metric.py
@@ -49,7 +49,7 @@ def jaccard_bits(bits1: np.ndarray, bits2: np.ndarray) -> float:
 	return 1. if union == 0 else intersection / union
 
 
-def jaccarddist_array(query: KmerSignature, refs: Sequence[KmerSignature], out: np.ndarray = None) -> np.ndarray:
+def jaccarddist_array(query: KmerSignature, refs: Sequence[KmerSignature], out: Optional[np.ndarray] = None) -> np.ndarray:
 	"""
 	Calculate Jaccard distances between a query k-mer signature and a list of reference signatures.