diff --git a/src/cmd/compile/internal/ssa/gen/ARM64.rules b/src/cmd/compile/internal/ssa/gen/ARM64.rules
index d9e614f61a..4c5f8c7502 100644
--- a/src/cmd/compile/internal/ssa/gen/ARM64.rules
+++ b/src/cmd/compile/internal/ssa/gen/ARM64.rules
@@ -574,8 +574,8 @@
 
 (EQ (CMPconst [0] z:(AND x y)) yes no) && z.Uses == 1 -> (EQ (TST x y) yes no)
 (NE (CMPconst [0] z:(AND x y)) yes no) && z.Uses == 1 -> (NE (TST x y) yes no)
-(EQ (CMPWconst [0] z:(AND x y)) yes no) && z.Uses == 1 -> (EQ (TST x y) yes no)
-(NE (CMPWconst [0] z:(AND x y)) yes no) && z.Uses == 1 -> (NE (TST x y) yes no)
+(EQ (CMPWconst [0] z:(AND x y)) yes no) && z.Uses == 1 -> (EQ (TSTW x y) yes no)
+(NE (CMPWconst [0] z:(AND x y)) yes no) && z.Uses == 1 -> (NE (TSTW x y) yes no)
 
 (EQ (CMPconst [0] x:(ANDconst [c] y)) yes no) && x.Uses == 1 -> (EQ (TSTconst [c] y) yes no)
 (NE (CMPconst [0] x:(ANDconst [c] y)) yes no) && x.Uses == 1 -> (NE (TSTconst [c] y) yes no)
diff --git a/src/cmd/compile/internal/ssa/rewriteARM64.go b/src/cmd/compile/internal/ssa/rewriteARM64.go
index cea9d03a9d..0715a5347d 100644
--- a/src/cmd/compile/internal/ssa/rewriteARM64.go
+++ b/src/cmd/compile/internal/ssa/rewriteARM64.go
@@ -32192,7 +32192,7 @@ func rewriteBlockARM64(b *Block) bool {
 		}
 		// match: (EQ (CMPWconst [0] z:(AND x y)) yes no)
 		// cond: z.Uses == 1
-		// result: (EQ (TST x y) yes no)
+		// result: (EQ (TSTW x y) yes no)
 		for {
 			v := b.Control
 			if v.Op != OpARM64CMPWconst {
@@ -32212,7 +32212,7 @@ func rewriteBlockARM64(b *Block) bool {
 				break
 			}
 			b.Kind = BlockARM64EQ
-			v0 := b.NewValue0(v.Pos, OpARM64TST, types.TypeFlags)
+			v0 := b.NewValue0(v.Pos, OpARM64TSTW, types.TypeFlags)
 			v0.AddArg(x)
 			v0.AddArg(y)
 			b.SetControl(v0)
@@ -33290,7 +33290,7 @@ func rewriteBlockARM64(b *Block) bool {
 		}
 		// match: (NE (CMPWconst [0] z:(AND x y)) yes no)
 		// cond: z.Uses == 1
-		// result: (NE (TST x y) yes no)
+		// result: (NE (TSTW x y) yes no)
 		for {
 			v := b.Control
 			if v.Op != OpARM64CMPWconst {
@@ -33310,7 +33310,7 @@ func rewriteBlockARM64(b *Block) bool {
 				break
 			}
 			b.Kind = BlockARM64NE
-			v0 := b.NewValue0(v.Pos, OpARM64TST, types.TypeFlags)
+			v0 := b.NewValue0(v.Pos, OpARM64TSTW, types.TypeFlags)
 			v0.AddArg(x)
 			v0.AddArg(y)
 			b.SetControl(v0)
diff --git a/test/fixedbugs/issue26438.go b/test/fixedbugs/issue26438.go
new file mode 100644
index 0000000000..d44da21eb0
--- /dev/null
+++ b/test/fixedbugs/issue26438.go
@@ -0,0 +1,26 @@
+// run
+
+// Copyright 2018 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.
+
+// Issue 26438: arm64 backend may use 64-bit TST for
+// "if uint32(a)&uint32(b) == 0", which should be
+// 32-bit TSTW
+
+package main
+
+//go:noinline
+func tstw(a, b uint64) uint64 {
+	if uint32(a)&uint32(b) == 0 {
+		return 100
+	} else {
+		return 200
+	}
+}
+
+func main() {
+	if tstw(0xff00000000, 0xaa00000000) == 200 {
+		panic("impossible")
+	}
+}