diff --git a/pybitcoin/merkle.py b/pybitcoin/merkle.py
index c558f38..22aae0b 100644
--- a/pybitcoin/merkle.py
+++ b/pybitcoin/merkle.py
@@ -60,7 +60,7 @@ def get(self, row_index, column_index):
         # check to make sure there are enough rows
         if row_index + 1 > len(self.rows):
             raise ValueError("There aren't that many rows.")
-        row = self.rows(row_index)
+        row = self.rows[row_index]
         # check to make sure there are enough items in the row
         if column_index + 1 > len(row):
             raise ValueError("There aren't that many items in that row.")
diff --git a/pybitcoin/transactions/utils.py b/pybitcoin/transactions/utils.py
index 1164355..7debc41 100644
--- a/pybitcoin/transactions/utils.py
+++ b/pybitcoin/transactions/utils.py
@@ -18,7 +18,7 @@ def count_bytes(hex_s):
     return len(hex_s)/2
 
 def flip_endian(s):
-    if is_hex:
+    if is_hex(s):
         return hexlify(unhexlify(s)[::-1])
     return s[::-1]
 
@@ -38,4 +38,4 @@ def variable_length_int(i):
     elif i < (2**64):
         return chr(255) + struct.pack('<Q', i) # pack into 8 bites
     else:
-        raise Exception('Integer cannot exceed 8 bytes in length.')
\ No newline at end of file
+        raise Exception('Integer cannot exceed 8 bytes in length.')