diff --git a/extract_otp_secret_keys.py b/extract_otp_secret_keys.py
index 51d3e6d..5dfa313 100644
--- a/extract_otp_secret_keys.py
+++ b/extract_otp_secret_keys.py
@@ -140,12 +140,15 @@ def extract_otps(args):
 
 def get_lines_from_file(filename):
     lines = read_lines_from_text_file(filename)
-    if lines != None:
+    if are_bytes(lines):
+        abort('\nBinary input was given in stdin, please use = instead of -.')
+    elif lines:
         return lines
 
     # could not process text file, try reading as image
     return convert_img_to_line(filename)
 
+
 def read_lines_from_text_file(filename):
     if filename != '=':
         check_file_exists(filename)
@@ -169,6 +172,7 @@ def read_lines_from_text_file(filename):
         finally:
             finput.close()
 
+
 def convert_img_to_line(filename):
     if filename != '-':
         try:
@@ -180,7 +184,10 @@ def convert_img_to_line(filename):
                 except AttributeError:
                     # Workaround for pytest, since pytest cannot monkeypatch sys.stdin.buffer
                     stdin = sys.stdin.read()
-                array = frombuffer(stdin, dtype='uint8')
+                try:
+                    array = frombuffer(stdin, dtype='uint8')
+                except TypeError as e:
+                    abort('\nERROR: Cannot read binary stdin buffer. Exception: {}'.format(str(e)))
                 image = imdecode(array, IMREAD_UNCHANGED)
 
             if image is None:
@@ -384,6 +391,16 @@ def check_file_exists(filename):
         abort('\nERROR: Input file provided is non-existent or not a file.'
         '\ninput file: {}'.format(filename))
 
+
+def are_bytes(lines):
+    if lines and len(lines) > 0:
+        try:
+            lines[0].startswith('#')
+            return False
+        except (UnicodeDecodeError, AttributeError, TypeError):
+            return True
+
+
 def eprint(*args, **kwargs):
     '''Print to stderr.'''
     print(*args, file=sys.stderr, **kwargs)
diff --git a/test_extract_otp_secret_keys_pytest.py b/test_extract_otp_secret_keys_pytest.py
index 99d8bf6..8d0e561 100644
--- a/test_extract_otp_secret_keys_pytest.py
+++ b/test_extract_otp_secret_keys_pytest.py
@@ -68,6 +68,25 @@ def test_extract_stdin_stdout(capsys, monkeypatch):
     assert captured.err == ''
 
 
+def test_extract_stdin_stdout_wrong_symbol(capsys, monkeypatch):
+    # Arrange
+    monkeypatch.setattr('sys.stdin', StringIO(read_file_to_str('example_export.txt')))
+
+    # Act
+    with raises(SystemExit) as e:
+        extract_otp_secret_keys.main(['='])
+
+    # Assert
+    captured = capsys.readouterr()
+
+    expected_stderr = "\nERROR: Cannot read binary stdin buffer. Exception: a bytes-like object is required, not 'str'\n"
+
+    assert captured.err == expected_stderr
+    assert captured.out == ''
+    assert e.value.code == 1
+    assert e.type == SystemExit
+
+
 def test_extract_csv(capsys):
     # Arrange
     cleanup()
@@ -534,6 +553,26 @@ Type:    totp
     assert captured.err == ''
 
 
+def test_img_qr_reader_from_stdin_wrong_symbol(capsys, monkeypatch):
+    # Arrange
+    # sys.stdin.buffer should be monkey patched, but it does not work
+    monkeypatch.setattr('sys.stdin', read_binary_file_as_stream('test/test_googleauth_export.png'))
+
+    # Act
+    with raises(SystemExit) as e:
+        extract_otp_secret_keys.main(['-'])
+
+    # Assert
+    captured = capsys.readouterr()
+
+    expected_stderr = '\nBinary input was given in stdin, please use = instead of -.\n'
+
+    assert captured.err == expected_stderr
+    assert captured.out == ''
+    assert e.value.code == 1
+    assert e.type == SystemExit
+
+
 def test_img_qr_reader_no_qr_code_in_image(capsys):
     # Act
     with raises(SystemExit) as e: