diff --git a/src/runtime/mbitmap.go b/src/runtime/mbitmap.go
index 4d39c321d8256b..efdcb8fca41fa8 100644
--- a/src/runtime/mbitmap.go
+++ b/src/runtime/mbitmap.go
@@ -978,8 +978,16 @@ func heapBitsSetType(x, size, dataSize uintptr, typ *_type) {
 			// nb unmodified: we just loaded 8 bits,
 			// and the next iteration will consume 8 bits,
 			// leaving us with the same nb the next time we're here.
-			b |= uintptr(*p) << nb
-			p = add1(p)
+			if nb < 8 {
+				b |= uintptr(*p) << nb
+				p = add1(p)
+			} else {
+				// Reduce the number of bits in b.
+				// This is important if we skipped
+				// over a scalar tail, since nb could
+				// be larger than the bit width of b.
+				nb -= 8
+			}
 		} else if p == nil {
 			// Almost as fast path: track bit count and refill from pbits.
 			// For short repetitions.
diff --git a/test/fixedbugs/issue11286.go b/test/fixedbugs/issue11286.go
new file mode 100644
index 00000000000000..560b7d4794251b
--- /dev/null
+++ b/test/fixedbugs/issue11286.go
@@ -0,0 +1,34 @@
+// run
+
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Test that pointer bitmaps of types with large scalar tails are
+// correctly repeated when unrolled into the heap bitmap.
+
+package main
+
+import "runtime"
+
+const D = 57
+
+type T struct {
+	a [D]float64
+	b map[string]int
+	c [D]float64
+}
+
+var ts []T
+
+func main() {
+	ts = make([]T, 4)
+	for i := range ts {
+		ts[i].b = make(map[string]int)
+	}
+	ts[3].b["abc"] = 42
+	runtime.GC()
+	if ts[3].b["abc"] != 42 {
+		panic("bad field value")
+	}
+}