diff --git a/src/potential/gmtgravmag3d.c b/src/potential/gmtgravmag3d.c
index 5246622bb8f..36124ab9e6b 100644
--- a/src/potential/gmtgravmag3d.c
+++ b/src/potential/gmtgravmag3d.c
@@ -362,7 +362,7 @@ static int parse(struct GMT_CTRL *GMT, struct GMTGRAVMAG3D_CTRL *Ctrl, struct GM
 						if (n_par < 4) err_npar = 1;
 						if (n_par < 7)  Ctrl->M.params[ELLIPSOID][nELL][6] = Ctrl->npts_circ;
 						if (n_par < 8)  Ctrl->M.params[ELLIPSOID][nELL][7] = Ctrl->n_slices;
-						if (Ctrl->M.params[SPHERE][nSPHERE][6] <= 0 || Ctrl->M.params[SPHERE][nSPHERE][7] <= 0) {
+						if (Ctrl->M.params[ELLIPSOID][nELL][6] <= 0 || Ctrl->M.params[ELLIPSOID][nELL][7] <= 0) {
 							GMT_Report (API, GMT_MSG_ERROR, "Bad parameters for the 'ellipsoid' body. Please, read the manual.");
 							return GMT_PARSE_ERROR;
 						}