diff --git a/cmd/show_test.go b/cmd/show_test.go
index 924c37176771da8f6a494c1a07359cd83adfdc16..732a0bdd426645533e488c13e16dee895113f46f 100644
--- a/cmd/show_test.go
+++ b/cmd/show_test.go
@@ -48,6 +48,7 @@ func TestShow(t *testing.T) {
   "string": "bar",
   "notAVal": "aVal",
   "notAnotherVal": "aVal2",
+	"filevar": "foo",
   "array": ["one", 2, [3]],
   "object": {"foo": "bar"}
 }
@@ -68,6 +69,7 @@ func TestShow(t *testing.T) {
 			filepath.FromSlash("../testdata/test.jsonnet"),
 			"-V", "aVar=aVal",
 			"-V", "anVar",
+			"--ext-str-file", "filevar=../testdata/extvar.file",
 		})
 
 		t.Log("output is", output)
diff --git a/testdata/extvar.file b/testdata/extvar.file
new file mode 100644
index 0000000000000000000000000000000000000000..19102815663d23f8b75a47e7a01965dcdc96468c
--- /dev/null
+++ b/testdata/extvar.file
@@ -0,0 +1 @@
+foo
\ No newline at end of file
diff --git a/testdata/test.jsonnet b/testdata/test.jsonnet
index fe1c002f5172e61cdff806a076b9a5aefdcfc7ee..0d5887e224eb44e76e999858cca2fceb22e03c18 100644
--- a/testdata/test.jsonnet
+++ b/testdata/test.jsonnet
@@ -1,6 +1,7 @@
 local test = import "test.libsonnet";
 local aVar = std.extVar("aVar");
 local anVar = std.extVar("anVar");
+local filevar = std.extVar("filevar");
 
 {
   apiVersion: "v1",
@@ -10,6 +11,7 @@ local anVar = std.extVar("anVar");
       string: "bar",
       notAVal : aVar,
       notAnotherVal : anVar,
+      filevar : filevar,
     }
   ],
 }