--- festival/speech_tools/siod/siod.cc.gcc7	2017-10-16 02:29:46.697359985 +0200
+++ festival/speech_tools/siod/siod.cc	2017-10-16 02:29:57.448296402 +0200
@@ -459,7 +459,7 @@
     matches = walloc(char *,siod_llength(lmatches)+1);
     for (l=lmatches,i=0; l; l=cdr(l),i++)
 	matches[i] = wstrdup(PNAME(car(l)));
-    matches[i] = '\0';
+    matches[i] = NULL;
 
     return matches;
 }
@@ -498,7 +498,7 @@
     matches = walloc(char *,siod_llength(lmatches)+1);
     for (l=lmatches,i=0; l; l=cdr(l),i++)
 	matches[i] = wstrdup(PNAME(car(l)));
-    matches[i] = '\0';
+    matches[i] = NULL;
 
     return matches;
 }