Index: src/pcb-printf.c
===================================================================
--- src/pcb-printf.c	(revision 10548)
+++ src/pcb-printf.c	(revision 10549)
@@ -164,7 +164,7 @@
 		value = value_local;
 
 	if (allow == 0)
-		allow = PCB_UNIT_ALLOW_ALL;
+		allow = PCB_UNIT_ALLOW_ALL_SANE;
 
 	i = printf_spec_->used + 64;
 	if (i > sizeof(printf_spec_new_local))
@@ -422,7 +422,7 @@
 	char tmp[128]; /* large enough for rendering a long long int */
 	int tmplen, retval = -1, slot_recursion = 0, mq_has_spec;
 	char *dot, *free_fmt = NULL;
-	enum pcb_allow_e mask = PCB_UNIT_ALLOW_ALL;
+	enum pcb_allow_e mask = PCB_UNIT_ALLOW_ALL_SANE;
 
 	gds_init(&spec);
 
@@ -644,7 +644,7 @@
 				case '2':
 				case 'D':
 					value[count++] = va_arg(args, pcb_coord_t);
-					if (CoordsToString(string, value, count, &spec, mask & PCB_UNIT_ALLOW_ALL, suffix) != 0) goto err;
+					if (CoordsToString(string, value, count, &spec, mask & PCB_UNIT_ALLOW_ALL_SANE, suffix) != 0) goto err;
 					break;
 				case 'd':
 					value[1] = va_arg(args, pcb_coord_t);
@@ -661,7 +661,7 @@
 							}
 						}
 						if (!found)
-							if (CoordsToString(string, value, 1, &spec, mask & PCB_UNIT_ALLOW_ALL, suffix) != 0) goto err;
+							if (CoordsToString(string, value, 1, &spec, mask & PCB_UNIT_ALLOW_ALL_SANE, suffix) != 0) goto err;
 					}
 					break;
 				case 'a':
@@ -700,7 +700,7 @@
 							}
 						}
 						if (!found)
-							if (CoordsToString(string, value, 1, &spec, PCB_UNIT_ALLOW_ALL, suffix) != 0) goto err;
+							if (CoordsToString(string, value, 1, &spec, PCB_UNIT_ALLOW_ALL_SANE, suffix) != 0) goto err;
 					}
 					break;
 				}
Index: src/unit.h
===================================================================
--- src/unit.h	(revision 10548)
+++ src/unit.h	(revision 10549)
@@ -49,7 +49,7 @@
 
 	PCB_UNIT_ALLOW_DMIL = 8192, /* for kicad legacy decimil units */
 
-	PCB_UNIT_ALLOW_METRIC = PCB_UNIT_ALLOW_NM | PCB_UNIT_ALLOW_DU | PCB_UNIT_ALLOW_UM | PCB_UNIT_ALLOW_MM | PCB_UNIT_ALLOW_CM | PCB_UNIT_ALLOW_M | PCB_UNIT_ALLOW_KM,
+	PCB_UNIT_ALLOW_METRIC = PCB_UNIT_ALLOW_NM  | PCB_UNIT_ALLOW_UM | PCB_UNIT_ALLOW_MM | PCB_UNIT_ALLOW_CM | PCB_UNIT_ALLOW_M | PCB_UNIT_ALLOW_KM,
 	PCB_UNIT_ALLOW_IMPERIAL = PCB_UNIT_ALLOW_DMIL | PCB_UNIT_ALLOW_CMIL | PCB_UNIT_ALLOW_MIL | PCB_UNIT_ALLOW_IN,
 	/* This is all units allowed in parse_l.l */
 #if 0
@@ -61,6 +61,9 @@
 	/* Used for pcb-printf %mS - should not include unusual units like km, cmil and dmil */
 	PCB_UNIT_ALLOW_NATURAL = PCB_UNIT_ALLOW_NM | PCB_UNIT_ALLOW_UM | PCB_UNIT_ALLOW_MM | PCB_UNIT_ALLOW_M | PCB_UNIT_ALLOW_MIL | PCB_UNIT_ALLOW_IN,
 
+	/* Allow all but the most exotic */
+	PCB_UNIT_ALLOW_ALL_SANE = ~(PCB_UNIT_ALLOW_DU | PCB_UNIT_ALLOW_DMIL),
+
 	PCB_UNIT_ALLOW_ALL = ~0
 };