http://bugs.gentoo.org/488626
http://bugzilla.xfce.org/show_bug.cgi?id=10417

--- src/task-manager-linux.c
+++ src/task-manager-linux.c
@@ -128,7 +128,7 @@
 	FILE *file;
 	gchar filename[96];
 	gint i;
-	gchar c;
+	gint c;
 
 	snprintf (filename, 96, "/proc/%i/cmdline", task->pid);
 	if ((file = fopen (filename, "r")) == NULL)
@@ -136,7 +136,7 @@
 
 	/* Read full command byte per byte until EOF */
 	for (i = 0; (c = fgetc (file)) != EOF && i < (gint)sizeof (task->cmdline) - 1; i++)
-		task->cmdline[i] = (c == '\0') ? ' ' : c;
+		task->cmdline[i] = (c == '\0') ? ' ' : (gchar)c;
 	task->cmdline[i] = '\0';
 	if (task->cmdline[i-1] == ' ')
 		task->cmdline[i-1] = '\0';