diff --git a/docs/sources/contributing/devenvironment.md b/docs/sources/contributing/devenvironment.md
index 607ed4d9ed..21d533686c 100644
--- a/docs/sources/contributing/devenvironment.md
+++ b/docs/sources/contributing/devenvironment.md
@@ -126,11 +126,13 @@ something like this
     PASS
     ok      github.com/docker/docker/utils        0.017s
 
-If $TESTFLAGS is set in the environment, it is passed as extra arguments
+If `$TESTFLAGS` is set in the environment, it will pass extra arguments
 to `go test`. You can use this to select certain tests to run, e.g.,
 
     $ TESTFLAGS='-test.run \^TestBuild\$' make test
 
+Only those test cases matching the regular expression inside quotation marks will be tested.
+
 If the output indicates "FAIL" and you see errors like this:
 
     server.go:1302 Error: Insertion failed because database is full: database or disk is full