diff --git a/sfs/fd/__init__.py b/sfs/fd/__init__.py
index 2d9555e4..1dfe2cb6 100644
--- a/sfs/fd/__init__.py
+++ b/sfs/fd/__init__.py
@@ -53,8 +53,7 @@ def synthesize(d, weights, ssd, secondary_source_function, **kwargs):
         This signature is expected::
 
             secondary_source_function(
-                position, normal_vector, weight, driving_function_weight,
-                **kwargs) -> numpy.ndarray
+                position, normal_vector, **kwargs) -> numpy.ndarray
 
     **kwargs
         All keyword arguments are forwarded to *secondary_source_function*.
diff --git a/sfs/td/__init__.py b/sfs/td/__init__.py
index 5efb20a5..a786ea54 100644
--- a/sfs/td/__init__.py
+++ b/sfs/td/__init__.py
@@ -37,8 +37,7 @@ def synthesize(signals, weights, ssd, secondary_source_function, **kwargs):
         This signature is expected::
 
             secondary_source_function(
-                position, normal_vector, weight, driving_signal,
-                **kwargs) -> numpy.ndarray
+                position, normal_vector, **kwargs) -> numpy.ndarray
 
     **kwargs
         All keyword arguments are forwarded to *secondary_source_function*.