diff --git a/book/super-example/main.go b/book/super-example/main.go
index b36aa6f8da..93c43590f4 100644
--- a/book/super-example/main.go
+++ b/book/super-example/main.go
@@ -53,7 +53,9 @@ func run(opts opts) wasm.Promise {
 		var r io.Reader
 		switch typ := opts.Input.Type(); typ {
 		case js.TypeString:
-			r = strings.NewReader(opts.Input.String())
+			if s := opts.Input.String(); strings.TrimSpace(s) != "" {
+				r = strings.NewReader(s)
+			}
 		case js.TypeObject:
 			if !opts.Input.InstanceOf(js.Global().Get("ReadableStream")) {
 				return nil, errInvalidInput
@@ -63,13 +65,15 @@ func run(opts opts) wasm.Promise {
 			return "", errInvalidInput
 		}
 		zctx := super.NewContext()
-		zr, err := anyio.NewReaderWithOpts(zctx, r, anyio.ReaderOpts{
-			Format: opts.InputFormat,
-		})
-		if err != nil {
-			return "", err
+		var readers []sio.Reader
+		if r != nil {
+			rc, err := anyio.NewReaderWithOpts(zctx, r, anyio.ReaderOpts{Format: opts.InputFormat})
+			if err != nil {
+				return "", err
+			}
+			defer rc.Close()
+			readers = []sio.Reader{rc}
 		}
-		defer zr.Close()
 		var buf bytes.Buffer
 		zwc, err := anyio.NewWriter(sio.NopCloser(&buf), anyio.WriterOpts{Format: opts.OutputFormat})
 		if err != nil {
@@ -78,7 +82,7 @@ func run(opts opts) wasm.Promise {
 		defer zwc.Close()
 		local := storage.NewLocalEngine()
 		comp := compiler.NewCompiler(local)
-		query, err := runtime.CompileQuery(context.Background(), zctx, comp, flowgraph, []sio.Reader{zr})
+		query, err := runtime.CompileQuery(context.Background(), zctx, comp, flowgraph, readers)
 		if err != nil {
 			return "", err
 		}
diff --git a/mdtest/mdtest.go b/mdtest/mdtest.go
index a47aa594c6..8edbdd2412 100644
--- a/mdtest/mdtest.go
+++ b/mdtest/mdtest.go
@@ -51,7 +51,9 @@
 // contains an SPQ test.  The content of the block must comprise three sections,
 // each preceeded by one or more "#"-prefixed lines.  The first section contains
 // an SPQ program, the second contains input provided to the program when the
-// test runs, and the third contains the program's expected output.
+// test runs, and the third contains the program's expected output.  If the
+// second section contains only whitespace, no input is provided when the test
+// runs.
 //
 // SPQ tests are run via the super command.  The command's exit status must
 // indicate success (i.e., be zero) unless the mdtest-spq block's info string
diff --git a/mdtest/test.go b/mdtest/test.go
index bc91b768ff..4ff5d9b39d 100644
--- a/mdtest/test.go
+++ b/mdtest/test.go
@@ -33,8 +33,11 @@ func (t *Test) Run() error {
 	}
 	var c *exec.Cmd
 	if t.SPQ != "" {
-		c = exec.Command("super", "-s", "-c", t.SPQ, "-")
-		c.Stdin = strings.NewReader(t.Input)
+		c = exec.Command("super", "-s", "-c", t.SPQ)
+		if s := t.Input; strings.TrimSpace(s) != "" {
+			c.Args = append(c.Args, "-")
+			c.Stdin = strings.NewReader(s)
+		}
 	} else {
 		c = exec.Command("bash", "-e", "-o", "pipefail")
 		c.Dir = t.Dir