diff --git a/NEWS.md b/NEWS.md
index 28e0098..9d4a8fb 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,3 +1,8 @@
+# 0.5.1
+- new `guess` logical parameter to `get_content_type()` to control 
+  whether it is used as a last resort passthrough (addresses #4)
+- updated external guess database
+
 # 0.5.0
 - {tidytest}
 - CRAN release
diff --git a/R/get-content-type.R b/R/get-content-type.R
index 262e56f..8b91754 100644
--- a/R/get-content-type.R
+++ b/R/get-content-type.R
@@ -10,12 +10,14 @@
 #'
 #' @md
 #' @param path path to a file
-#' @param ... passed on to [guess_content_type()]
+#' @param guess if `TRUE` (the default), calls [guess_content_type()] if
+#'        no internal rules match the magic header
+#' @param ... passed on to [guess_content_type()] if `guess` is `TRUE`
 #' @return character vector
 #' @export
 #' @examples
-#' get_content_type(system.file("extdat", "test.pdf", package="wand"))
-get_content_type <- function(path, ...) {
+#' get_content_type(system.file("extdat", "pass-through", "test.pdf", package="wand"))
+get_content_type <- function(path, guess = TRUE, ...) {
 
   path <- path.expand(path[1])
   if (!file.exists(path)) stop("File not found.", call.=FALSE)
@@ -28,9 +30,14 @@ get_content_type <- function(path, ...) {
   if (all(c(0xCA,0xFE,0xBA,0xBE) == hdr[1:4])) return("application/java-vm")
 
   if (all(c(0xD0,0xCF,0x11,0xE0,0xA1,0xB1,0x1A,0xE1) == hdr[1:8])) {
-    guessed_name <- guess_content_type(path)
-    if ((length(guessed_name) == 1) && (guessed_name != "???")) return(guessed_name)
+
+    if (guess) {
+      guessed_name <- guess_content_type(path)
+      if ((length(guessed_name) == 1) && (guessed_name != "???")) return(guessed_name)
+    }
+
     return("application/msword")
+
   }
 
   if (all(c(0x25,0x50,0x44,0x46,0x2d,0x31,0x2e) == hdr[1:7])) return("application/pdf")
@@ -107,8 +114,10 @@ get_content_type <- function(path, ...) {
     office_type <- check_office(hdr, path)
     if (length(office_type) > 0) return(office_type)
 
-    guessed_name <- guess_content_type(path)
-    if ((length(guessed_name) == 1) && (guessed_name != "???")) return(guessed_name)
+    if (guess) {
+      guessed_name <- guess_content_type(path)
+      if ((length(guessed_name) == 1) && (guessed_name != "???")) return(guessed_name)
+    }
 
     return("application/zip")
 
@@ -131,6 +140,7 @@ get_content_type <- function(path, ...) {
   if (all(c(0x00,0x00,0x01,0xBA) == hdr[1:4])) return("video/mpeg")
   if (all(c(0x00,0x00,0x01,0xB3) == hdr[1:4])) return("video/mpeg")
 
+  if (!guess) return("???")
 
   return(guess_content_type(path, ...))
 
diff --git a/R/guess-content-type.R b/R/guess-content-type.R
index 4381cd3..2397f25 100644
--- a/R/guess-content-type.R
+++ b/R/guess-content-type.R
@@ -16,7 +16,7 @@
 #' @return character vector
 #' @export
 #' @examples
-#' guess_content_type(system.file("extdat", "test.pdf", package="wand"))
+#' guess_content_type(system.file("extdat", "pass-through", "test.pdf", package="wand"))
 guess_content_type <- function(path, not_found = "???", custom_db = NULL) {
 
   path <- path.expand(path[1])
diff --git a/R/sysdata.rda b/R/sysdata.rda
index c564561..f5afff7 100644
Binary files a/R/sysdata.rda and b/R/sysdata.rda differ
diff --git a/inst/extdat/no-guess/csv.docx b/inst/extdat/no-guess/csv.docx
new file mode 100644
index 0000000..ccffa3b
--- /dev/null
+++ b/inst/extdat/no-guess/csv.docx
@@ -0,0 +1,3 @@
+Kid Name,Weight,Age
+Nakshatra,12,1.5
+Titas,16,6
diff --git a/inst/extdat/actions.csv b/inst/extdat/pass-through/actions.csv
similarity index 100%
rename from inst/extdat/actions.csv
rename to inst/extdat/pass-through/actions.csv
diff --git a/inst/extdat/actions.txt b/inst/extdat/pass-through/actions.txt
similarity index 100%
rename from inst/extdat/actions.txt
rename to inst/extdat/pass-through/actions.txt
diff --git a/inst/extdat/actions.xlsx b/inst/extdat/pass-through/actions.xlsx
similarity index 100%
rename from inst/extdat/actions.xlsx
rename to inst/extdat/pass-through/actions.xlsx
diff --git a/inst/extdat/test.au b/inst/extdat/pass-through/test.au
similarity index 100%
rename from inst/extdat/test.au
rename to inst/extdat/pass-through/test.au
diff --git a/inst/extdat/test.bin b/inst/extdat/pass-through/test.bin
similarity index 100%
rename from inst/extdat/test.bin
rename to inst/extdat/pass-through/test.bin
diff --git a/inst/extdat/test.bmp b/inst/extdat/pass-through/test.bmp
similarity index 100%
rename from inst/extdat/test.bmp
rename to inst/extdat/pass-through/test.bmp
diff --git a/inst/extdat/test.dtd b/inst/extdat/pass-through/test.dtd
similarity index 100%
rename from inst/extdat/test.dtd
rename to inst/extdat/pass-through/test.dtd
diff --git a/inst/extdat/test.emf b/inst/extdat/pass-through/test.emf
similarity index 100%
rename from inst/extdat/test.emf
rename to inst/extdat/pass-through/test.emf
diff --git a/inst/extdat/test.eps b/inst/extdat/pass-through/test.eps
similarity index 100%
rename from inst/extdat/test.eps
rename to inst/extdat/pass-through/test.eps
diff --git a/inst/extdat/test.fli b/inst/extdat/pass-through/test.fli
similarity index 100%
rename from inst/extdat/test.fli
rename to inst/extdat/pass-through/test.fli
diff --git a/inst/extdat/test.gif b/inst/extdat/pass-through/test.gif
similarity index 100%
rename from inst/extdat/test.gif
rename to inst/extdat/pass-through/test.gif
diff --git a/inst/extdat/test.ico b/inst/extdat/pass-through/test.ico
similarity index 100%
rename from inst/extdat/test.ico
rename to inst/extdat/pass-through/test.ico
diff --git a/inst/extdat/test.jpg b/inst/extdat/pass-through/test.jpg
similarity index 100%
rename from inst/extdat/test.jpg
rename to inst/extdat/pass-through/test.jpg
diff --git a/inst/extdat/test.mp3 b/inst/extdat/pass-through/test.mp3
similarity index 100%
rename from inst/extdat/test.mp3
rename to inst/extdat/pass-through/test.mp3
diff --git a/inst/extdat/test.odt b/inst/extdat/pass-through/test.odt
similarity index 100%
rename from inst/extdat/test.odt
rename to inst/extdat/pass-through/test.odt
diff --git a/inst/extdat/test.ogg b/inst/extdat/pass-through/test.ogg
similarity index 100%
rename from inst/extdat/test.ogg
rename to inst/extdat/pass-through/test.ogg
diff --git a/inst/extdat/test.pcx b/inst/extdat/pass-through/test.pcx
similarity index 100%
rename from inst/extdat/test.pcx
rename to inst/extdat/pass-through/test.pcx
diff --git a/inst/extdat/test.pdf b/inst/extdat/pass-through/test.pdf
similarity index 100%
rename from inst/extdat/test.pdf
rename to inst/extdat/pass-through/test.pdf
diff --git a/inst/extdat/test.pl b/inst/extdat/pass-through/test.pl
similarity index 100%
rename from inst/extdat/test.pl
rename to inst/extdat/pass-through/test.pl
diff --git a/inst/extdat/test.png b/inst/extdat/pass-through/test.png
similarity index 100%
rename from inst/extdat/test.png
rename to inst/extdat/pass-through/test.png
diff --git a/inst/extdat/test.pnm b/inst/extdat/pass-through/test.pnm
similarity index 100%
rename from inst/extdat/test.pnm
rename to inst/extdat/pass-through/test.pnm
diff --git a/inst/extdat/test.ppm b/inst/extdat/pass-through/test.ppm
similarity index 100%
rename from inst/extdat/test.ppm
rename to inst/extdat/pass-through/test.ppm
diff --git a/inst/extdat/test.ppt b/inst/extdat/pass-through/test.ppt
similarity index 100%
rename from inst/extdat/test.ppt
rename to inst/extdat/pass-through/test.ppt
diff --git a/inst/extdat/test.ps b/inst/extdat/pass-through/test.ps
similarity index 100%
rename from inst/extdat/test.ps
rename to inst/extdat/pass-through/test.ps
diff --git a/inst/extdat/test.psd b/inst/extdat/pass-through/test.psd
similarity index 100%
rename from inst/extdat/test.psd
rename to inst/extdat/pass-through/test.psd
diff --git a/inst/extdat/test.py b/inst/extdat/pass-through/test.py
similarity index 100%
rename from inst/extdat/test.py
rename to inst/extdat/pass-through/test.py
diff --git a/inst/extdat/test.rtf b/inst/extdat/pass-through/test.rtf
similarity index 100%
rename from inst/extdat/test.rtf
rename to inst/extdat/pass-through/test.rtf
diff --git a/inst/extdat/test.sh b/inst/extdat/pass-through/test.sh
similarity index 100%
rename from inst/extdat/test.sh
rename to inst/extdat/pass-through/test.sh
diff --git a/inst/extdat/test.tar b/inst/extdat/pass-through/test.tar
similarity index 100%
rename from inst/extdat/test.tar
rename to inst/extdat/pass-through/test.tar
diff --git a/inst/extdat/test.tar.gz b/inst/extdat/pass-through/test.tar.gz
similarity index 100%
rename from inst/extdat/test.tar.gz
rename to inst/extdat/pass-through/test.tar.gz
diff --git a/inst/extdat/test.tga b/inst/extdat/pass-through/test.tga
similarity index 100%
rename from inst/extdat/test.tga
rename to inst/extdat/pass-through/test.tga
diff --git a/inst/extdat/test.txt b/inst/extdat/pass-through/test.txt
similarity index 100%
rename from inst/extdat/test.txt
rename to inst/extdat/pass-through/test.txt
diff --git a/inst/extdat/test.txt.gz b/inst/extdat/pass-through/test.txt.gz
similarity index 100%
rename from inst/extdat/test.txt.gz
rename to inst/extdat/pass-through/test.txt.gz
diff --git a/inst/extdat/test.wav b/inst/extdat/pass-through/test.wav
similarity index 100%
rename from inst/extdat/test.wav
rename to inst/extdat/pass-through/test.wav
diff --git a/inst/extdat/test.wmf b/inst/extdat/pass-through/test.wmf
similarity index 100%
rename from inst/extdat/test.wmf
rename to inst/extdat/pass-through/test.wmf
diff --git a/inst/extdat/test.xcf b/inst/extdat/pass-through/test.xcf
similarity index 100%
rename from inst/extdat/test.xcf
rename to inst/extdat/pass-through/test.xcf
diff --git a/inst/extdat/test.xml b/inst/extdat/pass-through/test.xml
similarity index 100%
rename from inst/extdat/test.xml
rename to inst/extdat/pass-through/test.xml
diff --git a/inst/extdat/test.xpm b/inst/extdat/pass-through/test.xpm
similarity index 100%
rename from inst/extdat/test.xpm
rename to inst/extdat/pass-through/test.xpm
diff --git a/inst/extdat/test.zip b/inst/extdat/pass-through/test.zip
similarity index 100%
rename from inst/extdat/test.zip
rename to inst/extdat/pass-through/test.zip
diff --git a/inst/extdat/test_128_44_jstereo.mp3 b/inst/extdat/pass-through/test_128_44_jstereo.mp3
similarity index 100%
rename from inst/extdat/test_128_44_jstereo.mp3
rename to inst/extdat/pass-through/test_128_44_jstereo.mp3
diff --git a/inst/extdat/test_excel.xlsm b/inst/extdat/pass-through/test_excel.xlsm
similarity index 100%
rename from inst/extdat/test_excel.xlsm
rename to inst/extdat/pass-through/test_excel.xlsm
diff --git a/inst/extdat/test_excel.xlsx b/inst/extdat/pass-through/test_excel.xlsx
similarity index 100%
rename from inst/extdat/test_excel.xlsx
rename to inst/extdat/pass-through/test_excel.xlsx
diff --git a/inst/extdat/test_excel_2000.xls b/inst/extdat/pass-through/test_excel_2000.xls
similarity index 100%
rename from inst/extdat/test_excel_2000.xls
rename to inst/extdat/pass-through/test_excel_2000.xls
diff --git a/inst/extdat/test_excel_spreadsheet.xml b/inst/extdat/pass-through/test_excel_spreadsheet.xml
similarity index 100%
rename from inst/extdat/test_excel_spreadsheet.xml
rename to inst/extdat/pass-through/test_excel_spreadsheet.xml
diff --git a/inst/extdat/test_excel_web_archive.mht b/inst/extdat/pass-through/test_excel_web_archive.mht
similarity index 100%
rename from inst/extdat/test_excel_web_archive.mht
rename to inst/extdat/pass-through/test_excel_web_archive.mht
diff --git a/inst/extdat/test_nocompress.tif b/inst/extdat/pass-through/test_nocompress.tif
similarity index 100%
rename from inst/extdat/test_nocompress.tif
rename to inst/extdat/pass-through/test_nocompress.tif
diff --git a/inst/extdat/test_powerpoint.pptm b/inst/extdat/pass-through/test_powerpoint.pptm
similarity index 100%
rename from inst/extdat/test_powerpoint.pptm
rename to inst/extdat/pass-through/test_powerpoint.pptm
diff --git a/inst/extdat/test_powerpoint.pptx b/inst/extdat/pass-through/test_powerpoint.pptx
similarity index 100%
rename from inst/extdat/test_powerpoint.pptx
rename to inst/extdat/pass-through/test_powerpoint.pptx
diff --git a/inst/extdat/test_word.docm b/inst/extdat/pass-through/test_word.docm
similarity index 100%
rename from inst/extdat/test_word.docm
rename to inst/extdat/pass-through/test_word.docm
diff --git a/inst/extdat/test_word.docx b/inst/extdat/pass-through/test_word.docx
similarity index 100%
rename from inst/extdat/test_word.docx
rename to inst/extdat/pass-through/test_word.docx
diff --git a/inst/extdat/test_word_2000.doc b/inst/extdat/pass-through/test_word_2000.doc
similarity index 100%
rename from inst/extdat/test_word_2000.doc
rename to inst/extdat/pass-through/test_word_2000.doc
diff --git a/inst/extdat/test_word_6.0_95.doc b/inst/extdat/pass-through/test_word_6.0_95.doc
similarity index 100%
rename from inst/extdat/test_word_6.0_95.doc
rename to inst/extdat/pass-through/test_word_6.0_95.doc
diff --git a/inst/tinytest/test_wand.R b/inst/tinytest/test_wand.R
index d27a91e..7b8cda8 100644
--- a/inst/tinytest/test_wand.R
+++ b/inst/tinytest/test_wand.R
@@ -58,8 +58,12 @@ list(
   ), test.zip = "application/zip"
 ) -> results
 
-fils <- list.files(system.file("extdat", package="wand"), full.names=TRUE)
+fils <- list.files(system.file("extdat", "pass-through", package="wand"), full.names=TRUE)
 tst <- lapply(fils, get_content_type)
 names(tst) <- basename(fils)
 
 for(n in names(tst)) expect_identical(results[[n]], tst[[n]])
+
+no_guess <- system.file("extdat", "no-guess", "csv.docx", package = "wand")
+expect_equal(get_content_type(no_guess, guess = FALSE), "???")
+
diff --git a/man/get_content_type.Rd b/man/get_content_type.Rd
index 771e971..674ee1d 100644
--- a/man/get_content_type.Rd
+++ b/man/get_content_type.Rd
@@ -4,12 +4,15 @@
 \alias{get_content_type}
 \title{Discover MIME type of a file based on contents}
 \usage{
-get_content_type(path, ...)
+get_content_type(path, guess = TRUE, ...)
 }
 \arguments{
 \item{path}{path to a file}
 
-\item{...}{passed on to \code{\link[=guess_content_type]{guess_content_type()}}}
+\item{guess}{if \code{TRUE} (the default), calls \code{\link[=guess_content_type]{guess_content_type()}} if
+no internal rules match the magic header}
+
+\item{...}{passed on to \code{\link[=guess_content_type]{guess_content_type()}} if \code{guess} is \code{TRUE}}
 }
 \value{
 character vector
@@ -25,5 +28,5 @@ comparisons are required/desired. If no match is found, \code{???} is returned
 (see \code{\link[=guess_content_type]{guess_content_type()}} for how to override this behaviour).
 }
 \examples{
-get_content_type(system.file("extdat", "test.pdf", package="wand"))
+get_content_type(system.file("extdat", "pass-through", "test.pdf", package="wand"))
 }
diff --git a/man/guess_content_type.Rd b/man/guess_content_type.Rd
index f96d2d7..20db087 100644
--- a/man/guess_content_type.Rd
+++ b/man/guess_content_type.Rd
@@ -27,5 +27,5 @@ return one or more associated types for a given input path. If no match is
 found, \code{???} is returned.
 }
 \examples{
-guess_content_type(system.file("extdat", "test.pdf", package="wand"))
+guess_content_type(system.file("extdat", "pass-through", "test.pdf", package="wand"))
 }