diff --git a/pynmea2/nmea.py b/pynmea2/nmea.py
index a7c13d0..a6ef745 100644
--- a/pynmea2/nmea.py
+++ b/pynmea2/nmea.py
@@ -108,15 +108,16 @@ def parse(line, check=False):
         sentence_type   = match.group('sentence_type').upper()
         data            = data_str.split(',')
 
-        if checksum:
-            cs1 = int(checksum, 16)
-            cs2 = NMEASentence.checksum(nmea_str)
-            if cs1 != cs2:
+        if check:
+            if checksum:
+                cs1 = int(checksum, 16)
+                cs2 = NMEASentence.checksum(nmea_str)
+                if cs1 != cs2:
+                    raise ChecksumError(
+                        'checksum does not match: %02X != %02X' % (cs1, cs2), data)
+            else:
                 raise ChecksumError(
-                    'checksum does not match: %02X != %02X' % (cs1, cs2), data)
-        elif check:
-            raise ChecksumError(
-                'strict checking requested but checksum missing', data)
+                    'strict checking requested but checksum missing', data)
 
         talker_match = NMEASentence.talker_re.match(sentence_type)
         if talker_match:
diff --git a/pynmea2/stream.py b/pynmea2/stream.py
index 31970fb..8f4d3fb 100644
--- a/pynmea2/stream.py
+++ b/pynmea2/stream.py
@@ -9,7 +9,7 @@ class NMEAStreamReader(object):
     '''
     Reads NMEA sentences from a stream.
     '''
-    def __init__(self, stream=None, errors='raise'):
+    def __init__(self, stream=None, errors='raise', validate=True):
         '''
         Create NMEAStreamReader object.
 
@@ -23,6 +23,8 @@ def __init__(self, stream=None, errors='raise'):
                                 stream, and continue reading at the next line
             `'ignore'`          completely ignore and suppress the error, and
                                 continue reading at the next line
+
+        `validate`: If `False`, do not perform checksum validation on the incoming data.
         '''
 
         if errors not in ERRORS:
@@ -30,6 +32,7 @@ def __init__(self, stream=None, errors='raise'):
                     .format(ERRORS, errors))
 
         self.errors = errors
+        self.validate = validate
         self.stream = stream
         self.buffer = ''
 
@@ -50,7 +53,7 @@ def next(self, data=None):
 
         for line in lines:
             try:
-                msg = nmea.NMEASentence.parse(line)
+                msg = nmea.NMEASentence.parse(line, check=self.validate)
                 yield msg
             except nmea.ParseError as e:
                 if self.errors == 'raise':