diff --git a/appengine.go b/appengine.go
index 5db885b..9398160 100644
--- a/appengine.go
+++ b/appengine.go
@@ -36,10 +36,10 @@
 }
 
 // gaePrepContent returns a Reader that produces the content from the given
-// Reader, but strips the prefix "#appengine: " from each line. It also drops
-// any non-blank like that follows a series of 1 or more lines with the prefix.
+// Reader, but strips the prefix "#appengine:", optionally followed by a space, from each line.
+// It also drops any non-blank line that follows a series of 1 or more lines with the prefix.
 func gaePrepContent(in io.Reader) io.Reader {
-	var prefix = []byte("#appengine: ")
+	var prefix = []byte("#appengine:")
 	out, w := io.Pipe()
 	go func() {
 		r := bufio.NewReader(in)
@@ -52,6 +52,10 @@
 			}
 			if bytes.HasPrefix(b, prefix) {
 				b = b[len(prefix):]
+				if b[0] == ' ' {
+					// Consume a single space after the prefix.
+					b = b[1:]
+				}
 				drop = true
 			} else if drop {
 				if len(b) > 1 {
diff --git a/content/basics.article b/content/basics.article
index e124e1a..082a6ab 100644
--- a/content/basics.article
+++ b/content/basics.article
@@ -17,7 +17,7 @@
 #appengine: *Note:* The environment in which these programs are executed is
 #appengine: deterministic, so each time you run the example program
 #appengine: `rand.Intn` will return the same number.
-#appengine: 
+#appengine:
 #appengine: (To see a different number, seed the number generator; see [[https://golang.org/pkg/math/rand/#Seed][`rand.Seed`]].
 #appengine: Time is constant in the playground, so you will need to use something else as the seed.)
 
diff --git a/content/welcome.article b/content/welcome.article
index 7b318a7..fe512e7 100644
--- a/content/welcome.article
+++ b/content/welcome.article
@@ -70,41 +70,41 @@
 Click the [[javascript:highlightAndClick(".next-page")]["next"]] button or type `PageDown` to continue.
 
 #appengine: * Go offline
-#appengine: 
+#appengine:
 #appengine: This tour is also available as a stand-alone program that you can use
 #appengine: without access to the internet.
-#appengine: 
+#appengine:
 #appengine: The stand-alone tour is faster, as it builds and runs the code samples
 #appengine: on your own machine.
-#appengine: 
+#appengine:
 #appengine: To run the tour locally install and run the tour binary:
-#appengine: 
+#appengine:
 #appengine:   go get golang.org/x/tour
 #appengine:   tour
-#appengine: 
+#appengine:
 #appengine: The tour program will open a web browser displaying
 #appengine: your local version of the tour.
-#appengine: 
+#appengine:
 #appengine: Or, of course, you can continue to take the tour through this web site.
 
 #appengine: * The Go Playground
-#appengine: 
+#appengine:
 #appengine: This tour is built atop the [[https://play.golang.org/][Go Playground]], a
 #appengine: web service that runs on [[https://golang.org/][golang.org]]'s servers.
-#appengine: 
+#appengine:
 #appengine: The service receives a Go program, compiles, links, and runs the program inside
 #appengine: a sandbox, then returns the output.
-#appengine: 
+#appengine:
 #appengine: There are limitations to the programs that can be run in the playground:
-#appengine: 
+#appengine:
 #appengine: - In the playground the time begins at 2009-11-10 23:00:00 UTC (determining the significance of this date is an exercise for the reader). This makes it easier to cache programs by giving them deterministic output.
-#appengine: 
+#appengine:
 #appengine: - There are also limits on execution time and on CPU and memory usage, and the program cannot access external network hosts.
-#appengine: 
+#appengine:
 #appengine: The playground uses the latest stable release of Go.
-#appengine: 
+#appengine:
 #appengine: Read "[[https://blog.golang.org/playground][Inside the Go Playground]]" to learn more.
-#appengine: 
+#appengine:
 #appengine: .play welcome/sandbox.go
 
 * Congratulations