diff --git a/bilby/gw/conversion.py b/bilby/gw/conversion.py
index d405a7e0d01c05783a37663058e5b19aaa1cabad..50ce13756b55309f743570e79a2d3ba8189f7da2 100644
--- a/bilby/gw/conversion.py
+++ b/bilby/gw/conversion.py
@@ -251,7 +251,8 @@ def convert_to_lal_binary_black_hole_parameters(parameters):
     for angle in ['tilt_1', 'tilt_2', 'theta_jn']:
         cos_angle = str('cos_' + angle)
         if cos_angle in converted_parameters.keys():
-            converted_parameters[angle] = np.arccos(converted_parameters[cos_angle])
+            with np.errstate(invalid="ignore"):
+                converted_parameters[angle] = np.arccos(converted_parameters[cos_angle])
 
     if "delta_phase" in original_keys:
         with np.errstate(invalid="ignore"):