diff --git a/Lib/aifc.py b/Lib/aifc.py
index f4c196c..d8b7fab 100644
--- a/Lib/aifc.py
+++ b/Lib/aifc.py
@@ -486,7 +486,7 @@
                 try:
                     import cl
                 except ImportError:
-                    if self._comptype == 'ULAW':
+                    if self._comptype in ('ULAW', 'ulaw'):
                         try:
                             import audioop
                             self._convert = self._ulaw2lin
@@ -495,9 +495,9 @@
                         except ImportError:
                             pass
                     raise Error, 'cannot read compressed AIFF-C files'
-                if self._comptype == 'ULAW':
+                if self._comptype in ('ULAW', 'ulaw'):
                     scheme = cl.G711_ULAW
-                elif self._comptype == 'ALAW':
+                elif self._comptype in ('ALAW', 'alaw'):
                     scheme = cl.G711_ALAW
                 else:
                     raise Error, 'unsupported compression type'
@@ -654,7 +654,7 @@
     def setcomptype(self, comptype, compname):
         if self._nframeswritten:
             raise Error, 'cannot change parameters after starting to write'
-        if comptype not in ('NONE', 'ULAW', 'ALAW', 'G722'):
+        if comptype not in ('NONE', 'ULAW', 'ulaw', 'ALAW', 'alaw', 'G722'):
             raise Error, 'unsupported compression type'
         self._comptype = comptype
         self._compname = compname
@@ -674,7 +674,7 @@
         nchannels, sampwidth, framerate, nframes, comptype, compname = info
         if self._nframeswritten:
             raise Error, 'cannot change parameters after starting to write'
-        if comptype not in ('NONE', 'ULAW', 'ALAW', 'G722'):
+        if comptype not in ('NONE', 'ULAW', 'ulaw', 'ALAW', 'alaw', 'G722'):
             raise Error, 'unsupported compression type'
         self.setnchannels(nchannels)
         self.setsampwidth(sampwidth)
@@ -803,7 +803,7 @@
         try:
             import cl
         except ImportError:
-            if self._comptype == 'ULAW':
+            if self._comptype in ('ULAW', 'ulaw'):
                 try:
                     import audioop
                     self._convert = self._lin2ulaw
@@ -811,9 +811,9 @@
                 except ImportError:
                     pass
             raise Error, 'cannot write compressed AIFF-C files'
-        if self._comptype == 'ULAW':
+        if self._comptype in ('ULAW', 'ulaw'):
             scheme = cl.G711_ULAW
-        elif self._comptype == 'ALAW':
+        elif self._comptype in ('ALAW', 'alaw'):
             scheme = cl.G711_ALAW
         else:
             raise Error, 'unsupported compression type'
@@ -866,7 +866,7 @@
         _write_short(self._file, self._nchannels)
         self._nframes_pos = self._file.tell()
         _write_ulong(self._file, self._nframes)
-        if self._comptype in ('ULAW', 'ALAW', 'G722'):
+        if self._comptype in ('ULAW', 'ulaw', 'ALAW', 'alaw', 'G722'):
             _write_short(self._file, 8)
         else:
             _write_short(self._file, self._sampwidth * 8)
diff --git a/Lib/sunau.py b/Lib/sunau.py
index 4f0885a..31b280d 100644
--- a/Lib/sunau.py
+++ b/Lib/sunau.py
@@ -406,12 +406,15 @@
             self._patchheader()
 
     def close(self):
-        self._ensure_header_written()
-        if self._nframeswritten != self._nframes or \
-                  self._datalength != self._datawritten:
-            self._patchheader()
-        self._file.flush()
-        self._file = None
+        if self._file:
+            try:
+                self._ensure_header_written()
+                if self._nframeswritten != self._nframes or \
+                        self._datalength != self._datawritten:
+                    self._patchheader()
+                self._file.flush()
+            finally:
+                self._file = None
 
     #
     # private methods
diff --git a/Lib/wave.py b/Lib/wave.py
index 16b11dc..04a1a6d 100644
--- a/Lib/wave.py
+++ b/Lib/wave.py
@@ -436,11 +436,13 @@
 
     def close(self):
         if self._file:
-            self._ensure_header_written(0)
-            if self._datalength != self._datawritten:
-                self._patchheader()
-            self._file.flush()
-            self._file = None
+            try:
+                self._ensure_header_written(0)
+                if self._datalength != self._datawritten:
+                    self._patchheader()
+                self._file.flush()
+            finally:
+                self._file = None
         if self._i_opened_the_file:
             self._i_opened_the_file.close()
             self._i_opened_the_file = None
diff --git a/Misc/NEWS b/Misc/NEWS
index d23f7cc..ee4f001 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -32,6 +32,12 @@
 Library
 -------
 
+- Issue #18919: If the close() method of a writer in the sunau or wave module
+  failed, second invocation of close() and destructor no more raise an
+  exception.  Second invocation of close() on sunau writer now has no effects.
+  The aifc module now accepts lower case of names of the 'ulaw' and 'alaw'
+  codecs.
+
 - Issue #19131: The aifc module now correctly reads and writes sampwidth of
   compressed streams.