diff --git a/lisainstrument/instrument.py b/lisainstrument/instrument.py
index 76da94690ba30a25acf43fa5dd30431c78a5c6d9..2b088172cefc91f927b7ac59bdb98f2f7052a017 100644
--- a/lisainstrument/instrument.py
+++ b/lisainstrument/instrument.py
@@ -605,14 +605,14 @@ class Instrument:
         logger.debug("Propagating carrier fluctuations to distant MOSAs")
         carrier_fluctuations = \
             self.local_carrier_fluctuations \
-            - (self.central_freq + self.local_carrier_offsets) * self.distant_ttls / c
+            + (self.central_freq + self.local_carrier_offsets) * self.distant_ttls / c
         propagated_carrier_fluctuations = \
             (1 - self.d_pprs) * carrier_fluctuations.distant() \
             .transformed(lambda mosa, x: self.interpolate(x, -self.pprs[mosa]))
         self.distant_carrier_fluctuations = \
             propagated_carrier_fluctuations \
             + self.central_freq * self.gws \
-            - (self.central_freq + self.local_carrier_offsets) * self.local_ttls / c
+            + (self.central_freq + self.local_carrier_offsets) * self.local_ttls / c
 
         logger.debug("Propagating upper sideband offsets to distant MOSAs")
         self.distant_usb_offsets = \
@@ -623,14 +623,14 @@ class Instrument:
         logger.debug("Propagating upper sideband fluctuations to distant MOSAs")
         usb_fluctuations = \
             self.local_usb_fluctuations \
-            - (self.central_freq + self.local_usb_offsets) * self.distant_ttls / c
+            + (self.central_freq + self.local_usb_offsets) * self.distant_ttls / c
         propagated_usb_fluctuations = \
             (1 - self.d_pprs) * usb_fluctuations.distant() \
             .transformed(lambda mosa, x: self.interpolate(x, -self.pprs[mosa]))
         self.distant_usb_fluctuations = \
             propagated_usb_fluctuations \
             + self.central_freq * self.gws \
-            - (self.central_freq + self.local_usb_offsets) * self.local_ttls / c
+            + (self.central_freq + self.local_usb_offsets) * self.local_ttls / c
 
         logger.debug("Propagating timer deviations to distant MOSAs")
         self.distant_timer_deviations = \
@@ -1177,13 +1177,13 @@ class Instrument:
 
         logger.debug("Computing local tilt-to-length couplings")
         self.local_ttls = \
-         - self.ttl_coeffs_local_phis * self.mosa_total_jitter_phis \
-         - self.ttl_coeffs_local_etas * self.mosa_total_jitter_etas
+         self.ttl_coeffs_local_phis * self.mosa_total_jitter_phis \
+         + self.ttl_coeffs_local_etas * self.mosa_total_jitter_etas
 
         logger.debug("Computing unpropagated distant tilt-to-length couplings")
         self.distant_ttls = \
-         - self.ttl_coeffs_distant_phis * self.mosa_total_jitter_phis \
-         - self.ttl_coeffs_distant_etas * self.mosa_total_jitter_etas
+         self.ttl_coeffs_distant_phis * self.mosa_total_jitter_phis \
+         + self.ttl_coeffs_distant_etas * self.mosa_total_jitter_etas
 
     def lock_on_cavity(self, mosa):
         """Compute carrier and upper sideband offsets and fluctuations for laser locked on cavity.