Index: formats/format_wav_gsm.c
===================================================================
--- formats/format_wav_gsm.c	(revision 47521)
+++ formats/format_wav_gsm.c	(working copy)
@@ -86,6 +86,20 @@
 static char *desc = "Microsoft WAV format (Proprietary GSM)";
 static char *exts = "WAV|wav49";
 
+char gsm_silence[] = /* 33 */
+	{0xD8,0x20,0xA2,0xE1,0x5A,0x50,0x00,0x49,0x24,0x92,0x49,0x24,0x50,0x00,0x49
+	,0x24,0x92,0x49,0x24,0x50,0x00,0x49,0x24,0x92,0x49,0x24,0x50,0x00,0x49,0x24
+	,0x92,0x49,0x24};
+
+struct ast_frame silence_frame = {
+	.frametype = AST_FRAME_VOICE,
+	.subclass = AST_FORMAT_GSM,
+	.datalen = 33,
+	.mallocd = 0,
+	.src = "wav49",
+	.data = gsm_silence,
+};
+
 #if __BYTE_ORDER == __LITTLE_ENDIAN
 #define htoll(b) (b)
 #define htols(b) (b)
@@ -405,6 +419,8 @@
 	return tmp;
 }
 
+static int wav_write(struct ast_filestream *fs, struct ast_frame *f);
+
 static void wav_close(struct ast_filestream *s)
 {
 	char zero = 0;
@@ -415,6 +431,8 @@
 	glistcnt--;
 	ast_mutex_unlock(&wav_lock);
 	ast_update_use_count();
+	if (s->secondhalf)
+		wav_write(s, &silence_frame);
 	/* Pad to even length */
 	fseek(s->f, 0, SEEK_END);
 	if (ftell(s->f) & 0x1)