diff --git a/RELEASE_NOTES.rst b/RELEASE_NOTES.rst
index ec211cf3a..37af7ed33 100644
--- a/RELEASE_NOTES.rst
+++ b/RELEASE_NOTES.rst
@@ -27,6 +27,8 @@ Breaking changes:
 * ``Phaser.init()`` now disables all Kasli-oscillators. This avoids full power RF output being
   generated for some configurations.
 * Phaser: fixed coarse mixer frequency configuration
+* Mirny: Added extra delays in ``ADF5356.sync()``. This avoids the need of an extra delay before
+  calling `ADF5356.init()`.
 
 
 ARTIQ-6
diff --git a/artiq/coredevice/adf5356.py b/artiq/coredevice/adf5356.py
index dae2c97cb..845067541 100644
--- a/artiq/coredevice/adf5356.py
+++ b/artiq/coredevice/adf5356.py
@@ -236,6 +236,7 @@ class ADF5356:
         Write all registers to the device. Attempts to lock the PLL.
         """
         f_pfd = self.f_pfd()
+        delay(200 * us)         # Slack
 
         if f_pfd <= 75.0 * MHz:
             for i in range(13, 0, -1):
@@ -249,6 +250,7 @@ class ADF5356:
             n, frac1, (frac2_msb, frac2_lsb), (mod2_msb, mod2_lsb) = calculate_pll(
                 self.f_vco(), f_pfd >> 1
             )
+            delay(200 * us)     # Slack
 
             self.write(
                 13