diff --git a/src/begin.c b/src/begin.c
index 25826912f09..f7e391820e0 100644
--- a/src/begin.c
+++ b/src/begin.c
@@ -152,6 +152,8 @@ EXTERN_MSC int GMT_begin (void *V_API, int mode, void *args) {
 	/*----------------------- Standard module initialization and parsing ----------------------*/
 
 	if (API == NULL) return (GMT_NOT_A_SESSION);
+	if (gmt_modern_in_classic_session (API, "begin"))	/* If not command-line or external it means use of C API directly, so GMT_Create_Session needs to set modern mode first */
+		return (GMT_RUNTIME_ERROR);
 	if (mode == GMT_MODULE_PURPOSE) return (usage (API, GMT_MODULE_PURPOSE));	/* Return the purpose of program */
 	options = GMT_Create_Options (API, mode, args);	if (API->error) return (API->error);	/* Set or get option list */
 
diff --git a/src/end.c b/src/end.c
index c5001c456e6..3db3d06e076 100644
--- a/src/end.c
+++ b/src/end.c
@@ -96,6 +96,8 @@ EXTERN_MSC int GMT_end (void *V_API, int mode, void *args) {
 	/*----------------------- Standard module initialization and parsing ----------------------*/
 
 	if (API == NULL) return (GMT_NOT_A_SESSION);
+	if (gmt_modern_in_classic_session (API, "end"))	/* If not command-line or external it means use of C API directly, so GMT_Create_Session needs to set modern mode first */
+		return (GMT_RUNTIME_ERROR);
 	if (mode == GMT_MODULE_PURPOSE) return (usage (API, GMT_MODULE_PURPOSE));	/* Return the purpose of program */
 	options = GMT_Create_Options (API, mode, args);	if (API->error) return (API->error);	/* Set or get option list */
 
diff --git a/src/figure.c b/src/figure.c
index 69c6a2dec26..d2847365068 100644
--- a/src/figure.c
+++ b/src/figure.c
@@ -144,6 +144,8 @@ EXTERN_MSC int GMT_figure (void *V_API, int mode, void *args) {
 	/*----------------------- Standard module initialization and parsing ----------------------*/
 
 	if (API == NULL) return (GMT_NOT_A_SESSION);
+	if (gmt_modern_in_classic_session (API, "figure"))	/* If not command-line or external it means use of C API directly, so GMT_Create_Session needs to set modern mode first */
+		return (GMT_RUNTIME_ERROR);
 	if (mode == GMT_MODULE_PURPOSE) return (usage (API, GMT_MODULE_PURPOSE));	/* Return the purpose of program */
 	options = GMT_Create_Options (API, mode, args);	if (API->error) return (API->error);	/* Set or get option list */
 
diff --git a/src/gmt.c b/src/gmt.c
index 5a5390c331a..88f09a78ed4 100644
--- a/src/gmt.c
+++ b/src/gmt.c
@@ -83,7 +83,7 @@ int main (int argc, char *argv[]) {
 	gmt_main = !strcmp (module, PROGRAM_NAME);	/* true if running the main program, false otherwise */
 
 	/* Initialize new GMT session */
-	if ((api_ctrl = GMT_Create_Session (argv[0], GMT_PAD_DEFAULT, mode, NULL)) == NULL)
+	if ((api_ctrl = GMT_Create_Session (argv[0], GMT_PAD_DEFAULT, mode | GMT_SESSION_CMDLINE, NULL)) == NULL)
 		return GMT_RUNTIME_ERROR;
 
 	api_ctrl->internal = true;	/* This is a proper GMT commandline session (external programs will default to false) */
diff --git a/src/gmt_api.c b/src/gmt_api.c
index 4cac6adbc6a..b09d0f0b221 100644
--- a/src/gmt_api.c
+++ b/src/gmt_api.c
@@ -15942,3 +15942,12 @@ int64_t gmt_eliminate_duplicates (struct GMTAPI_CTRL *API, struct GMT_DATASET *D
 
 	return (n_dup);
 }
+
+bool gmt_modern_in_classic_session (struct GMTAPI_CTRL *API, const char *module) {
+	/* If not commandline or external it means use of C API directly, so GMT_Create_Session needs to set modern mode first */
+	if (API->runmode) return false;		/* Already in modern mode */
+	if (API->external) return false;	/* An external call from MATLAB, Julia, or Python */
+	if (API->cmdline) return false;		/* A standard command-line call via gmt program */
+	GMT_Report (API, GMT_MSG_ERROR, "Cannot call module \"%s\" in a classic session created via a call to GMT_Create_Session\n", module);
+	return true;	/* Sorry, calling a modern-mode only module from a classic session started from GMT_Create_Session in a C/C++ program is not allowed */
+}
\ No newline at end of file
diff --git a/src/gmt_constants.h b/src/gmt_constants.h
index e6a4cd30348..742171678a2 100644
--- a/src/gmt_constants.h
+++ b/src/gmt_constants.h
@@ -184,6 +184,8 @@ enum GMT_enum_basemap {
 	GMT_BASEMAP_ANNOT_BEFORE	= 0,
 	GMT_BASEMAP_ANNOT_AFTER		= 4};
 
+#define GMT_SESSION_CMDLINE	64	/* Passed when GMT_Create_Session is called from the command-line gmt.c driver only */
+
 /*! Handling of periodic data */
 enum GMT_time_period {
 	GMT_CYCLE_SEC = 1,
diff --git a/src/gmt_init.c b/src/gmt_init.c
index 185f0f00533..d3e331e898e 100644
--- a/src/gmt_init.c
+++ b/src/gmt_init.c
@@ -18342,8 +18342,29 @@ struct GMT_CTRL *gmt_begin (struct GMTAPI_CTRL *API, const char *session, unsign
 		return NULL;
 	}
 
+	/* Set up hash table for GMT_keywords (used in gmt_conf) */
+
+	if (gmt_hash_init (GMT, keys_hashnode, GMT_keywords, GMT_N_KEYS, GMT_N_KEYS)) {	/* Initialize hash table for GMT defaults */
+		gmtinit_free_GMT_ctrl (GMT);	/* Deallocate control structure */
+		return NULL;
+	}
+
+	/* Set up hash table for colornames (used to convert <colorname> to <r/g/b>) */
+
+	if (gmt_hash_init (GMT, GMT->session.rgb_hashnode, gmt_M_color_name, GMT_N_COLOR_NAMES, GMT_N_COLOR_NAMES)) {
+		gmtinit_free_GMT_ctrl (GMT);	/* Deallocate control structure */
+		return NULL;
+	}
+
 	GMT_Report (API, GMT_MSG_DEBUG, "Enter: gmt_manage_workflow\n");
-	if (gmt_manage_workflow (API, GMT_USE_WORKFLOW, NULL)) {
+	if (API->runmode && !API->external && !API->cmdline) {	/* Special case */
+		/* If external C call then there is no gmt.c driver and only one GMT_Create_Session, so we must init a new session here, if in modern mode */
+		mode = GMT_BEGIN_WORKFLOW;
+		GMT->current.setting.run_mode = GMT_MODERN;	/* Set here so we get the benefits of a "gmt module" initialization for PSL */
+	}
+	else	/* Regular use */
+		mode = GMT_USE_WORKFLOW;
+	if (gmt_manage_workflow (API, mode, NULL)) {
 		GMT_Report (API, GMT_MSG_ERROR, "Could not initialize the GMT workflow - Aborting.\n");
 		gmtinit_free_GMT_ctrl (GMT);	/* Deallocate control structure */
 		return NULL;
@@ -18384,7 +18405,7 @@ struct GMT_CTRL *gmt_begin (struct GMTAPI_CTRL *API, const char *session, unsign
 	gmt_reload_settings (GMT);	/* Initialize the standard GMT system default settings and overload with user's settings */
 	GMT_Report (API, GMT_MSG_DEBUG, "Exit:  gmt_reload_settings\n");
 
-	if (API->runmode) GMT->current.setting.run_mode = GMT_MODERN;	/* Enforced at API Creation */
+	if (API->runmode) GMT->current.setting.run_mode = GMT_MODERN;	/* Enforced at API Creation but set AFTER gmt_reload_settings */
 
 	/* There is no longer a -m option in GMT so multi segments are now always true.
 	   However, in GMT_COMPAT mode the -mi and -mo options WILL turn off multi in the other direction. */
@@ -18753,19 +18774,20 @@ GMT_LOCAL int gmtinit_get_graphics_formats (struct GMT_CTRL *GMT, char *formats,
 }
 
 GMT_LOCAL bool gmtinit_check_if_autosize (struct GMTAPI_CTRL *API, int ID) {
-	/* Check if the BoundingBox line in the half-baked PostScript file has max dimension (32767x32767)
+	/* Check if the BoundingBox line in the half-baked PostScript file has max dimension (GMT_PAPER_DIM x GMT_PAPER_DIM)
 	 * which we used to enforce automatic cropping to actual size [and possible extra margins] */
-	char file[PATH_MAX] = {""};
+	char file[PATH_MAX] = {""}, def_dim[GMT_LEN32] = {""};
 	FILE *fp;
 	snprintf (file, PATH_MAX, "%s/gmt_%d.ps-", API->gwf_dir, ID);	/* Current half-baked PostScript file */
 	if ((fp = fopen (file, "r")) == NULL) {	/* This is an unmitigated disaster */
 		GMT_Report (API, GMT_MSG_ERROR, "Failed to open half-baked PostScript file %s\n", file);
 		return false;
 	}
+	sprintf (def_dim, "%d %d", GMT_PAPER_DIM, GMT_PAPER_DIM);	/* Create the comparison string */
 	gmt_fgets (API->GMT, file, PATH_MAX, fp);	/* Skip first line */
 	gmt_fgets (API->GMT, file, PATH_MAX, fp);	/* Get second line with BoundingBox code */
 	fclose (fp);
-	if (strstr (file, "32767 32767")) return true;	/* Max paper size means auto-sized media */
+	if (strstr (file, def_dim)) return true;	/* Max paper size means auto-sized media */
 	return false;
 }
 
@@ -19578,7 +19600,7 @@ int gmt_manage_workflow (struct GMTAPI_CTRL *API, unsigned int mode, char *text)
 					gmtinit_setautopagesize (API->GMT);	/* Reset to auto */
 			}
 			snprintf (dir, PATH_MAX, "%s/%s", API->gwf_dir, GMT_SETTINGS_FILE);	/* Reuse dir string for saving gmt.conf to this dir */
-			API->GMT->current.setting.run_mode = GMT_MODERN;	/* Enable modern mode here so putdefaults can skip writing PS_MEDIA if not PostScript output */
+			API->GMT->current.setting.run_mode = GMT_MODERN;	/* Enable modern mode here AFTER gmt_conf call so putdefaults can skip writing PS_MEDIA if not PostScript output */
 			error = gmtinit_put_session_name (API, text);		/* Store session name, possibly setting psconvert options */
 			gmt_putdefaults (API->GMT, dir);		/* Write current GMT defaults to this sessions gmt.conf file in the workflow directory */
 			API->GMT->current.setting.history_orig = API->GMT->current.setting.history;	/* Temporarily turn off history so nothing is copied into the workflow dir */
diff --git a/src/gmt_private.h b/src/gmt_private.h
index b7249c78b20..e1b46e1c9cb 100644
--- a/src/gmt_private.h
+++ b/src/gmt_private.h
@@ -133,6 +133,7 @@ struct GMTAPI_CTRL {
 	int current_item[2];			/* Array number of current dataset being processed (in and out)*/
 	unsigned int pad;			/* Session default for number of rows/cols padding for grids [2] */
 	unsigned int external;			/* 1 if called via external API (MATLAB, Python) [0] */
+	unsigned int cmdline;			/* 1 if called via gmt.c [0] */
 	unsigned int runmode;			/* nonzero for GMT modern runmode [0 = classic] */
 	enum GMT_enum_fmt shape;		/* GMT_IS_COL_FORMAT (2) if column-major (MATLAB, Fortran), GMT_IS_ROW_FORMAT (1) if row-major (Python, C/C++) [1] */
 	unsigned int leave_grid_scaled;		/* 1 if we don't want to unpack a grid after we packed it for writing [0] */
diff --git a/src/gmt_prototypes.h b/src/gmt_prototypes.h
index 33a8c3b9dfb..b63504d7136 100644
--- a/src/gmt_prototypes.h
+++ b/src/gmt_prototypes.h
@@ -746,6 +746,7 @@ EXTERN_MSC void gmt_polar_to_cart (struct GMT_CTRL *GMT, double r, double theta,
 EXTERN_MSC void gmt_cart_to_polar (struct GMT_CTRL *GMT, double *r, double *theta, double *a, bool degrees);
 
 /* From gmt_api.c */
+EXTERN_MSC bool gmt_modern_in_classic_session (struct GMTAPI_CTRL *API, const char *module);
 EXTERN_MSC int64_t gmt_eliminate_duplicates (struct GMTAPI_CTRL *API, struct GMT_DATASET *D, uint64_t cols[], uint64_t ncols, bool text);
 EXTERN_MSC unsigned int gmt_whole_earth (struct GMT_CTRL *GMT, double we_in[], double we_out[]);
 EXTERN_MSC int gmt_copy (struct GMTAPI_CTRL *API, enum GMT_enum_family family, unsigned int direction, char *ifile, char *ofile);
diff --git a/src/inset.c b/src/inset.c
index b7f3ab510fe..5dd56815dde 100644
--- a/src/inset.c
+++ b/src/inset.c
@@ -257,6 +257,8 @@ EXTERN_MSC int GMT_inset (void *V_API, int mode, void *args) {
 	/*----------------------- Standard module initialization and parsing ----------------------*/
 
 	if (API == NULL) return (GMT_NOT_A_SESSION);
+	if (gmt_modern_in_classic_session (API, "inset"))	/* If not command-line or external it means use of C API directly, so GMT_Create_Session needs to set modern mode first */
+		return (GMT_RUNTIME_ERROR);
 	if (mode == GMT_MODULE_PURPOSE) return (usage (API, GMT_MODULE_PURPOSE));	/* Return the purpose of program */
 	options = GMT_Create_Options (API, mode, args);	if (API->error) return (API->error);	/* Set or get option list */
 
diff --git a/src/subplot.c b/src/subplot.c
index 789c183fa47..a594c87a7e0 100644
--- a/src/subplot.c
+++ b/src/subplot.c
@@ -839,6 +839,8 @@ EXTERN_MSC int GMT_subplot (void *V_API, int mode, void *args) {
 	/*----------------------- Standard module initialization and parsing ----------------------*/
 
 	if (API == NULL) return (GMT_NOT_A_SESSION);
+	if (gmt_modern_in_classic_session (API, "subplot"))	/* If not command-line or external it means use of C API directly, so GMT_Create_Session needs to set modern mode first */
+		return (GMT_RUNTIME_ERROR);
 	if (mode == GMT_MODULE_PURPOSE) return (usage (API, GMT_MODULE_PURPOSE));	/* Return the purpose of program */
 	options = GMT_Create_Options (API, mode, args);	if (API->error) return (API->error);	/* Set or get option list */
 
diff --git a/src/testapi_map.c b/src/testapi_map.c
new file mode 100644
index 00000000000..9b99f610577
--- /dev/null
+++ b/src/testapi_map.c
@@ -0,0 +1,29 @@
+#include "gmt.h"
+/* Used to examine https://github.com/GenericMappingTools/gmt/issues/4518
+ * Give an graphic extension to replicate that, otherwise we make a PS that can be
+ * compared with the original PS so the test can run as normal.
+ * Run testapi_map jpg to show the result is properly cropped.
+ * [add "| 458752" to GMT_SESSION_RUNMODE to simulate -Vd ]
+ */
+int main (int argc, char *argv[]) {
+	void *API;
+
+	/* Initialize the GMT session */
+	if ((API = GMT_Create_Session ("GMT_plot", 2, GMT_SESSION_RUNMODE, NULL)) == NULL)
+		return EXIT_FAILURE;
+	if (argc > 1) {	/* Gave a particular graphics format (we hope - no checking here) */
+		char string[64] = {""};
+		sprintf (string, "apimap %s", argv[1]);
+		GMT_Call_Module (API, "begin", GMT_MODULE_CMD, string);
+	}
+	else	/* Default to PostScript */
+		GMT_Call_Module (API, "begin", GMT_MODULE_CMD, "apimap ps");
+	GMT_Call_Module (API, "basemap", GMT_MODULE_CMD, "-BWESN -Bxa30mg30m -Bya20mg20m -JM7.27/42.27/15c -R5.5/41.425/9.0/43.1r");
+	if (argc > 1)
+		GMT_Call_Module (API, "end", GMT_MODULE_CMD, "show");
+	else
+		GMT_Call_Module (API, "end", GMT_MODULE_CMD, NULL);
+	/* Destroy session */
+	if (GMT_Destroy_Session (API)) 
+		return EXIT_FAILURE;
+}
diff --git a/test/api/apimap.ps b/test/api/apimap.ps
new file mode 100644
index 00000000000..8a68fe3e6ac
Binary files /dev/null and b/test/api/apimap.ps differ
diff --git a/test/api/apimap.sh b/test/api/apimap.sh
new file mode 100755
index 00000000000..abed0911e29
--- /dev/null
+++ b/test/api/apimap.sh
@@ -0,0 +1,6 @@
+#!/usr/bin/env bash
+#
+# Test the C API for simulating a modern mode basemap plot
+# See https://github.com/GenericMappingTools/gmt/issues/4518
+ps=apimap.ps
+testapi_map > $ps
diff --git a/test/gmtest.in b/test/gmtest.in
index 4cc4235d99e..c1d25d95635 100755
--- a/test/gmtest.in
+++ b/test/gmtest.in
@@ -110,6 +110,7 @@ for apiprog in \
     testapi_cube \
     testapi_makecpt \
     testapi_matrix \
+    testapi_map \
     testapi_matrix_pad \
     testapi_matrix_plot \
     testapi_mixmatrix \