diff --git a/src/emu/chan.c b/src/emu/chan.c
index 092ed9b..ed6d8bb 100644
--- a/src/emu/chan.c
+++ b/src/emu/chan.c
@@ -63,22 +63,6 @@ set_dirty(struct chan *chan)
 	return 0;
 }
 
-static int
-check_duplicates(struct chan *chan, struct value *v)
-{
-	/* If duplicates are allowed just skip the check */
-	if (chan->prop[CHAN_ALLOW_DUP])
-		return 0;
-
-	if (value_is_equal(&chan->last_value, v)) {
-		err("%s: same value as last_value %s",
-				chan->name, value_str(chan->last_value));
-		return -1;
-	}
-
-	return 0;
-}
-
 int
 chan_set(struct chan *chan, struct value value)
 {
@@ -92,9 +76,19 @@ chan_set(struct chan *chan, struct value value)
 		return -1;
 	}
 
-	if (check_duplicates(chan, &value) != 0) {
-		err("%s: cannot set duplicated value", chan->name);
-		return -1;
+	/* If duplicates are allowed just skip the check */
+	if (!chan->prop[CHAN_ALLOW_DUP]) {
+		if (value_is_equal(&chan->last_value, &value)) {
+			if (chan->prop[CHAN_IGNORE_DUP]) {
+				dbg("%s: value already set to %s",
+						chan->name, value_str(value));
+				return 0;
+			} else {
+				err("%s: same value as last_value %s",
+						chan->name, value_str(chan->last_value));
+				return -1;
+			}
+		}
 	}
 
 	dbg("%s: sets value to %s", chan->name, value_str(value));
@@ -127,9 +121,19 @@ chan_push(struct chan *chan, struct value value)
 		return -1;
 	}
 
-	if (check_duplicates(chan, &value) != 0) {
-		err("%s: cannot push a duplicated value", chan->name);
-		return -1;
+	/* If duplicates are allowed just skip the check */
+	if (!chan->prop[CHAN_ALLOW_DUP]) {
+		if (value_is_equal(&chan->last_value, &value)) {
+			if (chan->prop[CHAN_IGNORE_DUP]) {
+				dbg("%s: value already set to %s",
+						chan->name, value_str(value));
+				return 0;
+			} else {
+				err("%s: same value as last_value %s",
+						chan->name, value_str(chan->last_value));
+				return -1;
+			}
+		}
 	}
 
 	struct chan_stack *stack = &chan->data.stack;
diff --git a/src/emu/chan.h b/src/emu/chan.h
index 1ef377e..7b6a63d 100644
--- a/src/emu/chan.h
+++ b/src/emu/chan.h
@@ -19,6 +19,7 @@ enum chan_type {
 enum chan_prop {
 	CHAN_DIRTY_WRITE = 0,
 	CHAN_ALLOW_DUP,
+	CHAN_IGNORE_DUP,
 	CHAN_MAXPROP,
 };
 
diff --git a/test/unit/chan.c b/test/unit/chan.c
index 1fbbe2a..8d10d30 100644
--- a/test/unit/chan.c
+++ b/test/unit/chan.c
@@ -41,6 +41,8 @@ test_dirty(void)
 
 	if (chan_flush(&chan) != 0)
 		die("chan_flush failed\n");
+
+	err("OK");
 }
 
 static void
@@ -72,10 +74,14 @@ test_single(void)
 
 	if (!value_is_equal(&value, &one))
 		die("chan_read returned unexpected value\n");
+
+	err("OK");
 }
 
+/* Test that writting the same value to a channel raises an error, but not if we
+ * set the CHAN_ALLOW_DUP flag */
 static void
-test_duplicate(void)
+test_allow_dup(void)
 {
 	struct chan chan;
 	chan_init(&chan, CHAN_SINGLE, "testchan");
@@ -90,12 +96,44 @@ test_duplicate(void)
 	if (chan_set(&chan, value_int64(1)) == 0)
 		die("chan_set didn't fail\n");
 
-	/* Now enable duplicates */
+	/* Allow duplicates */
 	chan_prop_set(&chan, CHAN_ALLOW_DUP, 1);
 
 	/* Then it should allow writting the same value */
 	if (chan_set(&chan, value_int64(1)) != 0)
 		die("chan_set failed\n");
+
+	/* Also ensure the channel is dirty */
+	if (!chan.is_dirty)
+		die("chan is not dirty");
+
+	err("OK");
+}
+
+/* Test that writting the same value to a channel with the flag CHAN_IGNORE_DUP,
+ * causes the channel to remain clean (without the is_dirty flag set) */
+static void
+test_ignore_dup(void)
+{
+	struct chan chan;
+	chan_init(&chan, CHAN_SINGLE, "testchan");
+	chan_prop_set(&chan, CHAN_IGNORE_DUP, 1);
+
+	if (chan_set(&chan, value_int64(1)) != 0)
+		die("chan_set failed\n");
+
+	if (chan_flush(&chan) != 0)
+		die("chan_flush failed\n");
+
+	/* Write the same value */
+	if (chan_set(&chan, value_int64(1)) != 0)
+		die("chan_set failed");
+
+	/* And ensure the channel is not dirty */
+	if (chan.is_dirty)
+		die("chan is dirty");
+
+	err("OK");
 }
 
 //static void
@@ -159,7 +197,8 @@ int main(void)
 {
 	test_single();
 	test_dirty();
-	test_duplicate();
+	test_allow_dup();
+	test_ignore_dup();
 	//test_stack();
 	return 0;
 }