diff -r 454b97887c5a Lib/aifc.py
--- a/Lib/aifc.py	Fri Dec 02 19:49:02 2011 +0200
+++ b/Lib/aifc.py	Fri Dec 30 13:01:18 2011 +0400
@@ -716,18 +716,12 @@
 
     def _ensure_header_written(self, datasize):
         if not self._nframeswritten:
-            if self._comptype in (b'ULAW', b'ALAW'):
+            if self._comptype in (b'ULAW', b'ulaw', b'ALAW', b'alaw', b'G722'):
                 if not self._sampwidth:
                     self._sampwidth = 2
                 if self._sampwidth != 2:
                     raise Error('sample width must be 2 when compressing '
-                                'with ulaw/ULAW or alaw/ALAW')
-            if self._comptype == b'G722':
-                if not self._sampwidth:
-                    self._sampwidth = 2
-                if self._sampwidth != 2:
-                    raise Error('sample width must be 2 when compressing '
-                                'with G7.22 (ADPCM)')
+                                'with ulaw/ULAW, alaw/ALAW or G7.22 (ADPCM)')
             if not self._nchannels:
                 raise Error('# channels not specified')
             if not self._sampwidth:
@@ -743,8 +737,6 @@
             self._convert = self._lin2ulaw
         elif self._comptype in (b'alaw', b'ALAW'):
             self._convert = self._lin2alaw
-        else:
-            raise Error('unsupported compression type')
 
     def _write_header(self, initlength):
         if self._aifc and self._comptype != b'NONE':
diff -r 454b97887c5a Lib/test/test_aifc.py
--- a/Lib/test/test_aifc.py	Fri Dec 02 19:49:02 2011 +0200
+++ b/Lib/test/test_aifc.py	Fri Dec 30 13:01:18 2011 +0400
@@ -1,6 +1,7 @@
 from test.support import findfile, run_unittest, TESTFN
 import unittest
 import os
+import io
 
 import aifc
 
@@ -109,6 +110,16 @@
         f.close()
         self.assertEqual(testfile.closed, True)
 
+    def test_write_header_comptype_sampwidth(self):
+        for comptype in (b'ULAW', b'ulaw', b'ALAW', b'alaw', b'G722'):
+            fout = self.fout = aifc.open(io.BytesIO(), 'wb')
+            fout.setnchannels(1)
+            fout.setframerate(1)
+            fout.setcomptype(comptype, b'')
+            fout.close()
+            self.assertEqual(fout.getsampwidth(), 2)
+            fout.initfp(None)
+
 
 def test_main():
     run_unittest(AIFCTest)