diff --git a/man/incant.Rd b/man/incant.Rd
index 5fff68f..6ee2386 100644
--- a/man/incant.Rd
+++ b/man/incant.Rd
@@ -4,10 +4,14 @@
 \alias{incant}
 \title{Retrieve 'magic' attributes from files and directories}
 \usage{
-incant(path)
+incant(path, magic_db = NA_character_)
 }
 \arguments{
 \item{path}{character vector of files to use magic on}
+
+\item{magic_db}{either \code{NULL} (the default) to use the built-in
+\code{magic.mgc} database or an atomic character vector with a
+colon-separated list of full paths to custom \code{magic.mgc} database(s).}
 }
 \value{
 a \code{tibble} / \code{data.frame} of file magic attributes.
@@ -27,4 +31,8 @@ system.file("img", package="filemagic") \%>\%
   incant() \%>\%
   glimpse()
 }
+\references{
+See \url{http://openpreservation.org/blog/2012/08/09/magic-editing-and-creation-primer/}
+  for information on how to create your own \code{magic.mgc} databases.
+}
 
diff --git a/src/wand.cpp b/src/wand.cpp
index 2e3f5dc..3b5a5c6 100644
--- a/src/wand.cpp
+++ b/src/wand.cpp
@@ -30,6 +30,8 @@ DataFrame incant(CharacterVector path) {
   StringVector extensions(input_size);
   StringVector description(input_size);
 
+  const char *mtype = NULL;
+
   for (unsigned int i=0; i<input_size; i++) {
 
     if ((i % 10000) == 0) Rcpp::checkUserInterrupt();
@@ -42,7 +44,7 @@ DataFrame incant(CharacterVector path) {
     if (cookie == NULL) {
       mime_type[i] = NA_STRING;
     } else {
-      magic_load(cookie, NULL);
+      magic_load(cookie, mtype);
       const char *magic_result = magic_file(cookie, fullPath.c_str());
       if (magic_result == NULL) {
         mime_type[i] = NA_STRING;
@@ -57,7 +59,7 @@ DataFrame incant(CharacterVector path) {
     if (cookie == NULL) {
       encoding[i] = NA_STRING;
     } else {
-      magic_load(cookie, NULL);
+      magic_load(cookie, mtype);
       const char *magic_result = magic_file(cookie, fullPath.c_str());
       if (magic_result == NULL) {
         encoding[i] = NA_STRING;
@@ -72,7 +74,7 @@ DataFrame incant(CharacterVector path) {
     if (cookie == NULL) {
       extensions[i] = NA_STRING;
     } else {
-      magic_load(cookie, NULL);
+      magic_load(cookie, mtype);
       const char *magic_result = magic_file(cookie, fullPath.c_str());
       if (magic_result == NULL) {
         extensions[i] = NA_STRING;
@@ -87,7 +89,7 @@ DataFrame incant(CharacterVector path) {
     if (cookie == NULL) {
       description[i] = NA_STRING;
     } else {
-      magic_load(cookie, NULL);
+      magic_load(cookie, mtype);
       const char *magic_result = magic_file(cookie, fullPath.c_str());
       if (magic_result == NULL) {
         description[i] = NA_STRING;