diff --git a/src/runtime/iface_test.go b/src/runtime/iface_test.go
index 7f27baa..6d8f861 100644
--- a/src/runtime/iface_test.go
+++ b/src/runtime/iface_test.go
@@ -29,6 +29,20 @@
 func (TL) Method1() {}
 func (TL) Method2() {}
 
+type T8 uint8
+type T16 uint16
+type T32 uint32
+type T64 uint64
+type Tstr string
+type Tslice []byte
+
+func (T8) Method1()     {}
+func (T16) Method1()    {}
+func (T32) Method1()    {}
+func (T64) Method1()    {}
+func (Tstr) Method1()   {}
+func (Tslice) Method1() {}
+
 var (
 	e  interface{}
 	e_ interface{}
@@ -261,3 +275,129 @@
 		t.Fatalf("want 0 allocs, got %v", n)
 	}
 }
+
+func TestZeroConvT2x(t *testing.T) {
+	tests := []struct {
+		name string
+		fn   func()
+	}{
+		{name: "E8", fn: func() { e = eight8 }},  // any byte-sized value does not allocate
+		{name: "E16", fn: func() { e = zero16 }}, // zero values do not allocate
+		{name: "E32", fn: func() { e = zero32 }},
+		{name: "E64", fn: func() { e = zero64 }},
+		{name: "Estr", fn: func() { e = zerostr }},
+		{name: "Eslice", fn: func() { e = zeroslice }},
+		{name: "Econstflt", fn: func() { e = 99.0 }}, // constants do not allocate
+		{name: "Econststr", fn: func() { e = "change" }},
+		{name: "I8", fn: func() { i1 = eight8I }},
+		{name: "I16", fn: func() { i1 = zero16I }},
+		{name: "I32", fn: func() { i1 = zero32I }},
+		{name: "I64", fn: func() { i1 = zero64I }},
+		{name: "Istr", fn: func() { i1 = zerostrI }},
+		{name: "Islice", fn: func() { i1 = zerosliceI }},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			n := testing.AllocsPerRun(1000, test.fn)
+			if n != 0 {
+				t.Errorf("want zero allocs, got %v", n)
+			}
+		})
+	}
+}
+
+var (
+	eight8  uint8 = 8
+	eight8I T8    = 8
+
+	zero16  uint16 = 0
+	zero16I T16    = 0
+	one16   uint16 = 1
+
+	zero32  uint32 = 0
+	zero32I T32    = 0
+	one32   uint32 = 1
+
+	zero64  uint64 = 0
+	zero64I T64    = 0
+	one64   uint64 = 1
+
+	zerostr  string = ""
+	zerostrI Tstr   = ""
+	nzstr    string = "abc"
+
+	zeroslice  []byte = nil
+	zerosliceI Tslice = nil
+	nzslice    []byte = []byte("abc")
+
+	zerobig [512]byte
+	nzbig   [512]byte = [512]byte{511: 1}
+)
+
+func BenchmarkConvT2Ezero(b *testing.B) {
+	b.Run("zero", func(b *testing.B) {
+		b.Run("16", func(b *testing.B) {
+			for i := 0; i < b.N; i++ {
+				e = zero16
+			}
+		})
+		b.Run("32", func(b *testing.B) {
+			for i := 0; i < b.N; i++ {
+				e = zero32
+			}
+		})
+		b.Run("64", func(b *testing.B) {
+			for i := 0; i < b.N; i++ {
+				e = zero64
+			}
+		})
+		b.Run("str", func(b *testing.B) {
+			for i := 0; i < b.N; i++ {
+				e = zerostr
+			}
+		})
+		b.Run("slice", func(b *testing.B) {
+			for i := 0; i < b.N; i++ {
+				e = zeroslice
+			}
+		})
+		b.Run("big", func(b *testing.B) {
+			for i := 0; i < b.N; i++ {
+				e = zerobig
+			}
+		})
+	})
+	b.Run("nonzero", func(b *testing.B) {
+		b.Run("16", func(b *testing.B) {
+			for i := 0; i < b.N; i++ {
+				e = one16
+			}
+		})
+		b.Run("32", func(b *testing.B) {
+			for i := 0; i < b.N; i++ {
+				e = one32
+			}
+		})
+		b.Run("64", func(b *testing.B) {
+			for i := 0; i < b.N; i++ {
+				e = one64
+			}
+		})
+		b.Run("str", func(b *testing.B) {
+			for i := 0; i < b.N; i++ {
+				e = nzstr
+			}
+		})
+		b.Run("slice", func(b *testing.B) {
+			for i := 0; i < b.N; i++ {
+				e = nzslice
+			}
+		})
+		b.Run("big", func(b *testing.B) {
+			for i := 0; i < b.N; i++ {
+				e = nzbig
+			}
+		})
+	})
+}