diff --git a/src/imas_mex_casts.c b/src/imas_mex_casts.c
index d2e997f..eaaf2db 100644
--- a/src/imas_mex_casts.c
+++ b/src/imas_mex_casts.c
@@ -274,6 +274,11 @@ al_status_t castCellToChar(mxArray ** data)
 
   numel = mxGetNumberOfElements(cellData);
 
+  if (numel == 0) {
+    *data = NULL;
+    return status;
+  }
+
   strings = malloc(numel*sizeof(char *));
   for (i = 0; i < numel; i++) {
     cell = mxGetCell(*data, (mwIndex) i);
diff --git a/src/imas_mex_utils.c b/src/imas_mex_utils.c
index 3f63550..ceaecc9 100644
--- a/src/imas_mex_utils.c
+++ b/src/imas_mex_utils.c
@@ -975,6 +975,7 @@ al_status_t my_al_write_data(struct imas_mex_actionInfo * action, struct imas_me
 	if (field->datatype == CHAR_DATA && field->dim == 2) {
 		if (mxIsCell(data)) {
 			if (status.code >= 0) status = cast_status = castCellToChar((mxArray **) &data);
+			if (data == NULL) return (al_status_t) {0,""};
 		}
 	}