diff --git a/SFS_monochromatic/driving_functions_mono/driving_function_mono_wfs_ps.m b/SFS_monochromatic/driving_functions_mono/driving_function_mono_wfs_ps.m
index d7f882f2..c540f5f0 100644
--- a/SFS_monochromatic/driving_functions_mono/driving_function_mono_wfs_ps.m
+++ b/SFS_monochromatic/driving_functions_mono/driving_function_mono_wfs_ps.m
@@ -142,7 +142,7 @@
         % r = |x0-xs|
         r = vector_norm(x0-xs,2);
         % driving signal
-        D = -1/(2c) .* 1i*omega/c * vector_product(x0-xs,nx0,2) ./ r .* besselh(1,2,omega/c*r);
+        D = -1/(2*c) .* 1i*omega/c * vector_product(x0-xs,nx0,2) ./ r .* besselh(1,2,omega/c*r);
         %
         %
     elseif strcmp('delft1988',driving_functions)