diff --git a/sum.go b/sum.go
index 9d61950..d6bf2f9 100644
--- a/sum.go
+++ b/sum.go
@@ -65,10 +65,7 @@ func Sum(data []byte, code uint64, length int) (Multihash, error) {
 	return Encode(d, code)
 }
 
-func sumBlake2s(data []byte, size int) ([]byte, error) {
-	if size != 32 {
-		return nil, fmt.Errorf("unsupported length for blake2s: %d", size)
-	}
+func sumBlake2s32(data []byte, _ int) ([]byte, error) {
 	d := blake2s.Sum256(data)
 	return d[:], nil
 }
@@ -209,12 +206,9 @@ func registerNonStdlibHashFuncs() {
 
 	// Blake family of hash functions
 	// BLAKE2S
-	for c := uint64(BLAKE2S_MIN); c <= BLAKE2S_MAX; c++ {
-		size := int(c - BLAKE2S_MIN + 1)
-		RegisterHashFunc(c, func(buf []byte, _ int) ([]byte, error) {
-			return sumBlake2s(buf, size)
-		})
-	}
+	//
+	// We only support 32byte (256 bit)
+	RegisterHashFunc(BLAKE2S_MIN+31, sumBlake2s32)
 	// BLAKE2B
 	for c := uint64(BLAKE2B_MIN); c <= BLAKE2B_MAX; c++ {
 		size := int(c - BLAKE2B_MIN + 1)
diff --git a/sum_test.go b/sum_test.go
index 3226b00..37e256c 100644
--- a/sum_test.go
+++ b/sum_test.go
@@ -181,3 +181,18 @@ func TestTooLargeLength(t *testing.T) {
 		t.Fatal("bad error", err)
 	}
 }
+
+func TestBasicSum(t *testing.T) {
+	for code, name := range Codes {
+		defaultLen, ok := DefaultLengths[code]
+		if !ok {
+			defaultLen = 32
+		}
+		_, err := Sum([]byte("test"), code, defaultLen)
+		switch err {
+		case ErrSumNotSupported, nil:
+		default:
+			t.Errorf("unexpected error for %s: %s", name, err)
+		}
+	}
+}