diff --git a/src/io/multi.go b/src/io/multi.go
index 46e45a60e8b7f3..d784846862c455 100644
--- a/src/io/multi.go
+++ b/src/io/multi.go
@@ -4,13 +4,19 @@
 
 package io
 
+type eofReader struct{}
+
+func (eofReader) Read([]byte) (int, error) {
+	return 0, EOF
+}
+
 type multiReader struct {
 	readers []Reader
 }
 
 func (mr *multiReader) Read(p []byte) (n int, err error) {
 	for len(mr.readers) > 0 {
-		// Optimization to flatten nested multiReaders (Issue 13558)
+		// Optimization to flatten nested multiReaders (Issue 13558).
 		if len(mr.readers) == 1 {
 			if r, ok := mr.readers[0].(*multiReader); ok {
 				mr.readers = r.readers
@@ -19,7 +25,9 @@ func (mr *multiReader) Read(p []byte) (n int, err error) {
 		}
 		n, err = mr.readers[0].Read(p)
 		if err == EOF {
-			mr.readers[0] = nil // permit earlier GC
+			// Use eofReader instead of nil to avoid nil panic
+			// after performing flatten (Issue 18232).
+			mr.readers[0] = eofReader{} // permit earlier GC
 			mr.readers = mr.readers[1:]
 		}
 		if n > 0 || err != EOF {
diff --git a/src/io/multi_test.go b/src/io/multi_test.go
index 16e351a87911ec..1a6292fa8ac2c5 100644
--- a/src/io/multi_test.go
+++ b/src/io/multi_test.go
@@ -264,3 +264,27 @@ func TestMultiReaderFreesExhaustedReaders(t *testing.T) {
 		t.Fatalf(`ReadFull = %d (%q), %v; want 2, "ar", nil`, n, buf[:n], err)
 	}
 }
+
+func TestInterleavedMultiReader(t *testing.T) {
+	r1 := strings.NewReader("123")
+	r2 := strings.NewReader("45678")
+
+	mr1 := MultiReader(r1, r2)
+	mr2 := MultiReader(mr1)
+
+	buf := make([]byte, 4)
+
+	// Have mr2 use mr1's []Readers.
+	// Consume r1 (and clear it for GC to handle) and consume part of r2.
+	n, err := ReadFull(mr2, buf)
+	if got := string(buf[:n]); got != "1234" || err != nil {
+		t.Errorf(`ReadFull(mr2) = (%q, %v), want ("1234", nil)`, got, err)
+	}
+
+	// Consume the rest of r2 via mr1.
+	// This should not panic even though mr2 cleared r1.
+	n, err = ReadFull(mr1, buf)
+	if got := string(buf[:n]); got != "5678" || err != nil {
+		t.Errorf(`ReadFull(mr1) = (%q, %v), want ("5678", nil)`, got, err)
+	}
+}