diff --git a/src/swiftest/swiftest_sph.f90 b/src/swiftest/swiftest_sph.f90
index 1c0f5962d..726948177 100644
--- a/src/swiftest/swiftest_sph.f90
+++ b/src/swiftest/swiftest_sph.f90
@@ -30,7 +30,7 @@ module subroutine swiftest_sph_g_acc_one(GMcb, r_0, phi, theta, rh, c_lm, g_sph,
         real(DP), intent(in)        :: theta                       !! Inclination/Zenith angle (radians)
         real(DP), intent(in), dimension(:)          :: rh          !! distance vector of body
         real(DP), intent(in), dimension(:, :, :)    :: c_lm        !! Spherical Harmonic coefficients
-        real(DP), intent(out), dimension(:)         :: g_sph       !! acceleration vector
+        real(DP), intent(out), dimension(NDIM)         :: g_sph       !! acceleration vector
         real(DP), intent(in),  optional :: GMpl                    !! Mass of input body if it is not a test particle
         real(DP), dimension(:),   intent(inout), optional :: aoblcb  !! Barycentric acceleration of central body (only for massive input bodies)