diff --git a/lib/database.cc b/lib/database.cc
index 98f101e6..f1a9dc2e 100644
--- a/lib/database.cc
+++ b/lib/database.cc
@@ -1447,7 +1447,7 @@ _notmuch_database_link_message_to_parents (notmuch_database_t *notmuch,
     keys = g_hash_table_get_keys (parents);
     for (l = keys; l; l = l->next) {
 	char *parent_message_id;
-	const char *parent_thread_id;
+	const char *parent_thread_id = NULL;
 
 	parent_message_id = (char *) l->data;
 
diff --git a/notmuch-new.c b/notmuch-new.c
index bfb46001..3512de72 100644
--- a/notmuch-new.c
+++ b/notmuch-new.c
@@ -67,7 +67,7 @@ handle_sigint (unused (int sig))
 {
     static char msg[] = "Stopping...         \n";
 
-    write(2, msg, sizeof(msg)-1);
+    (void) write(2, msg, sizeof(msg)-1);
     interrupted = 1;
 }
 
diff --git a/notmuch-show.c b/notmuch-show.c
index 8da3295e..19fb49f2 100644
--- a/notmuch-show.c
+++ b/notmuch-show.c
@@ -866,7 +866,7 @@ do_show_single (void *ctx,
 
 	while (!feof (file)) {
 	    size = fread (buf, 1, sizeof (buf), file);
-	    fwrite (buf, size, 1, stdout);
+	    (void) fwrite (buf, size, 1, stdout);
 	}
 
 	fclose (file);
diff --git a/notmuch-tag.c b/notmuch-tag.c
index 537d5a4d..292c5da3 100644
--- a/notmuch-tag.c
+++ b/notmuch-tag.c
@@ -26,7 +26,7 @@ static void
 handle_sigint (unused (int sig))
 {
     static char msg[] = "Stopping...         \n";
-    write(2, msg, sizeof(msg)-1);
+    (void) write(2, msg, sizeof(msg)-1);
     interrupted = 1;
 }