diff --git a/src/gmt_api.c b/src/gmt_api.c
index 7a929776e56..1a3fb2536d5 100644
--- a/src/gmt_api.c
+++ b/src/gmt_api.c
@@ -3980,9 +3980,11 @@ GMT_LOCAL struct GMT_DATASET * gmtapi_import_dataset (struct GMTAPI_CTRL *API, i
 				if ((V_obj = S_obj->resource) == NULL) {
 					gmt_M_free (GMT, D_obj);	return_null (API, GMT_PTR_IS_NULL);
 				}
-				if (V_obj->type[0] != GMT_DOUBLE) {
-					GMT_Report (API, GMT_MSG_ERROR, "Only double-precision vectors can be passed via reference to datasets\n");
-					gmt_M_free (GMT, D_obj);	return_null (API, GMT_NOT_A_VALID_TYPE);
+				for (col = 0; col < V_obj->n_columns; col++) {
+					if (V_obj->type[col] != GMT_DOUBLE) {
+						GMT_Report (API, GMT_MSG_ERROR, "Only double-precision vectors can be passed via reference to datasets\n");
+						gmt_M_free (GMT, D_obj);	return_null (API, GMT_NOT_A_VALID_TYPE);
+					}
 				}
 				VH = gmt_get_V_hidden (V_obj);
 				if (GMT->common.q.mode == GMT_RANGE_ROW_IN || GMT->common.q.mode == GMT_RANGE_DATA_IN)
@@ -4009,7 +4011,7 @@ GMT_LOCAL struct GMT_DATASET * gmtapi_import_dataset (struct GMTAPI_CTRL *API, i
 					else
 						col_pos = col_pos_out = col;	/* Just goto that column */
 					S->data[col_pos_out] = V_obj->data[col_pos].f8;
-					SH->alloc_mode[col_pos_out] = VH->alloc_mode[col];	/* Inherit from what we got */
+					SH->alloc_mode[col_pos_out] = GMT_ALLOC_EXTERNALLY;	/* Not this objects job to free what was passed in by reference */
 				}
 				DH = gmt_get_DD_hidden (D_obj);
 				if (smode) S->text = V_obj->text;
@@ -7646,7 +7648,7 @@ GMT_LOCAL int gmtapi_init_import (struct GMTAPI_CTRL *API, enum GMT_enum_family
 					return_value (API, API->error, GMT_NOTSET);	/* Failure to register */
 				}
 				n_reg++;	/* Count of new items registered */
-				gmt_M_free (API->GMT, wesn);
+				if (API->GMT->common.R.active[RSET]) gmt_M_free (API->GMT, wesn);
 				if (first_ID == GMT_NOTSET) first_ID = object_ID;	/* Found our first ID */
 				if ((item = gmtlib_validate_id (API, family, object_ID, GMT_IN, GMTAPI_MODULE_INPUT)) == GMT_NOTSET)
 					return_value (API, API->error, GMT_NOTSET);	/* Some internal error... */
diff --git a/src/testapi_vector_times.c b/src/testapi_vector_times.c
new file mode 100644
index 00000000000..d97c8e14607
--- /dev/null
+++ b/src/testapi_vector_times.c
@@ -0,0 +1,28 @@
+#include "gmt.h"
+int main () {
+	void *API = NULL;                 /* The API control structure */
+	struct GMT_VECTOR *V = NULL;	  /* Structure to hold input dataset as vectors */
+	char input[GMT_VF_LEN] = {""};     			/* String to hold virtual input filename */
+	char args[128] = {""};            			/* String to hold module command arguments */
+
+	uint64_t dim[4] = {2, 4, 1, 0};
+	char *x[4] = {"2021-03-01", "2021-03-02", "2021-03-03", "2021-03-04"};
+	double y[4] = {0.0, 1.0, 2.0, 3.0};
+
+	/* Initialize the GMT session */
+	API = GMT_Create_Session ("test", 2U, GMT_SESSION_EXTERNAL, NULL);
+	/* Create a dataset */
+	if ((V = GMT_Create_Data (API, GMT_IS_DATASET|GMT_VIA_VECTOR, GMT_IS_POINT, GMT_CONTAINER_ONLY, dim, NULL, NULL, 0, 0, NULL)) == NULL) return (EXIT_FAILURE);
+	/**/
+	GMT_Put_Vector(API, V, 0, GMT_TEXT, x);
+	GMT_Put_Vector(API, V, 1, GMT_DOUBLE, y);
+	/* Associate our data table with a virtual file */
+	GMT_Open_VirtualFile (API, GMT_IS_DATASET|GMT_VIA_VECTOR, GMT_IS_POINT, GMT_IN|GMT_IS_REFERENCE, V, input);
+	/* Prepare the module arguments */
+	sprintf (args, "%s -JX10c/5c -R2021-03-01/2021-03-04/-0.1/30 -Baf -BWSen -P", input);
+	/* Call the psxy module */
+	GMT_Call_Module (API, "psxy", GMT_MODULE_CMD, args);
+	GMT_Close_VirtualFile (API, input);
+	/* Destroy the GMT session */
+	if (GMT_Destroy_Session (API)) return EXIT_FAILURE;
+};
diff --git a/test/api/apivectortimes.sh b/test/api/apivectortimes.sh
new file mode 100755
index 00000000000..9f05fa58398
--- /dev/null
+++ b/test/api/apivectortimes.sh
@@ -0,0 +1,6 @@
+#!/usr/bin/env bash
+#
+# Test the C API for plotting datetimes
+# See https://github.com/GenericMappingTools/gmt/pull/6521
+ps=apivectortimes.ps
+testapi_vector_times > $ps
diff --git a/test/baseline/api.dvc b/test/baseline/api.dvc
index 8aa20efe4a3..31a11242be3 100644
--- a/test/baseline/api.dvc
+++ b/test/baseline/api.dvc
@@ -1,5 +1,5 @@
 outs:
-- md5: 5bd99a34dd32a31bbfeb4336a9e445b7.dir
-  size: 3017982
-  nfiles: 15
+- md5: b985dda50abc7f6dcceb4a8848e0a83a.dir
+  size: 3041741
+  nfiles: 16
   path: api
diff --git a/test/gmtest.in b/test/gmtest.in
index a7e62df6839..f8ed2dab03c 100755
--- a/test/gmtest.in
+++ b/test/gmtest.in
@@ -123,6 +123,7 @@ for apiprog in \
     testapi_matrix_as_grid \
     testapi_vector_strings \
     testapi_vector_plot \
+    testapi_vector_times \
     testapi_vector_io \
     testapi_matrix_io \
     testapi_matrix_360 \