diff --git a/sys/dev/acpica/acpi_resource.c b/sys/dev/acpica/acpi_resource.c
index 669e693f0c73..51c30e591d8a 100644
--- a/sys/dev/acpica/acpi_resource.c
+++ b/sys/dev/acpica/acpi_resource.c
@@ -504,6 +504,51 @@ struct acpi_res_context {
     void 	*ar_parent;
 };
 
+/*
+ * Add a resource to the device's resource list.  We define our own function
+ * for this since bus_set_resource() doesn't handle duplicates of any kind.
+ *
+ * XXX This should be merged into resource_list_add() eventually.
+ */
+static int
+acpi_reslist_add(device_t dev, int type, int rid, u_long start, u_long count)
+{
+    struct resource_list_entry *rle;
+    struct resource_list *rl;
+    u_long end;
+    
+    end = start + count - 1;
+    rl = BUS_GET_RESOURCE_LIST(device_get_parent(dev), dev);
+
+    /*
+     * Loop through all current resources to see if the new one overlaps
+     * any existing ones.  If so, the old one always takes precedence and
+     * the new one is adjusted (or rejected).  We check for three cases:
+     *
+     * 1. Tail of new resource overlaps head of old resource:  truncate the
+     *    new resource so it is contiguous with the start of the old.
+     * 2. New resource wholly contained within the old resource:  error.
+     * 3. Head of new resource overlaps tail of old resource:  truncate the
+     *    new resource so it is contiguous, following the old.
+     */
+    SLIST_FOREACH(rle, rl, link) {
+	if (rle->type == type) {
+	    if (start < rle->start && end >= rle->start) {
+		count = rle->start - start;
+		break;
+	    } else if (start >= rle->start && start <= rle->end) {
+		if (end > rle->end) {
+		    start = rle->end + 1;
+		    count = end - rle->end + 1;
+		    break;
+		} else 
+		    return (EEXIST);
+	    }
+	}
+    }
+    return (bus_set_resource(dev, type, rid, start, count));
+}
+
 static void
 acpi_res_set_init(device_t dev, void *arg, void **context)
 {
@@ -534,7 +579,7 @@ acpi_res_set_ioport(device_t dev, void *context, u_int32_t base,
 
     if (cp == NULL)
 	return;
-    bus_set_resource(dev, SYS_RES_IOPORT, cp->ar_nio++, base, length);
+    acpi_reslist_add(dev, SYS_RES_IOPORT, cp->ar_nio++, base, length);
 }
 
 static void
@@ -557,7 +602,7 @@ acpi_res_set_memory(device_t dev, void *context, u_int32_t base,
     if (cp == NULL)
 	return;
 
-    bus_set_resource(dev, SYS_RES_MEMORY, cp->ar_nmem++, base, length);
+    acpi_reslist_add(dev, SYS_RES_MEMORY, cp->ar_nmem++, base, length);
 }
 
 static void
@@ -584,7 +629,7 @@ acpi_res_set_irq(device_t dev, void *context, u_int32_t *irq, int count,
     if (count != 1)
 	return;
 
-    bus_set_resource(dev, SYS_RES_IRQ, cp->ar_nirq++, *irq, 1);
+    acpi_reslist_add(dev, SYS_RES_IRQ, cp->ar_nirq++, *irq, 1);
 }
 
 static void
@@ -599,7 +644,7 @@ acpi_res_set_drq(device_t dev, void *context, u_int32_t *drq, int count)
     if (count != 1)
 	return;
 
-    bus_set_resource(dev, SYS_RES_DRQ, cp->ar_ndrq++, *drq, 1);
+    acpi_reslist_add(dev, SYS_RES_DRQ, cp->ar_ndrq++, *drq, 1);
 }
 
 static void