diff --git a/src/cmd/compile/internal/ssa/gen/AMD64.rules b/src/cmd/compile/internal/ssa/gen/AMD64.rules
index 408678f054..8a253035e0 100644
--- a/src/cmd/compile/internal/ssa/gen/AMD64.rules
+++ b/src/cmd/compile/internal/ssa/gen/AMD64.rules
@@ -1274,8 +1274,8 @@
 (CMPQconst (ANDQconst _ [m]) [n]) && 0 <= m && m < n => (FlagLT_ULT)
 (CMPQconst (ANDLconst _ [m]) [n]) && 0 <= m && m < n => (FlagLT_ULT)
 (CMPLconst (ANDLconst _ [m]) [n]) && 0 <= m && m < n => (FlagLT_ULT)
-(CMPWconst (ANDLconst _ [m]) [n]) && 0 <= m && int16(m) < n => (FlagLT_ULT)
-(CMPBconst (ANDLconst _ [m]) [n]) && 0 <= m && int8(m)  < n => (FlagLT_ULT)
+(CMPWconst (ANDLconst _ [m]) [n]) && 0 <= int16(m) && int16(m) < n => (FlagLT_ULT)
+(CMPBconst (ANDLconst _ [m]) [n]) && 0 <= int8(m)  && int8(m)  < n => (FlagLT_ULT)
 
 // TESTQ c c sets flags like CMPQ c 0.
 (TESTQconst [c] (MOVQconst [d])) && int64(c) == d && c == 0 => (FlagEQ)
diff --git a/src/cmd/compile/internal/ssa/rewriteAMD64.go b/src/cmd/compile/internal/ssa/rewriteAMD64.go
index 3d7eb8c9a4..32ef26f98d 100644
--- a/src/cmd/compile/internal/ssa/rewriteAMD64.go
+++ b/src/cmd/compile/internal/ssa/rewriteAMD64.go
@@ -6886,7 +6886,7 @@ func rewriteValueAMD64_OpAMD64CMPBconst(v *Value) bool {
 		return true
 	}
 	// match: (CMPBconst (ANDLconst _ [m]) [n])
-	// cond: 0 <= m && int8(m) < n
+	// cond: 0 <= int8(m) && int8(m) < n
 	// result: (FlagLT_ULT)
 	for {
 		n := auxIntToInt8(v.AuxInt)
@@ -6894,7 +6894,7 @@ func rewriteValueAMD64_OpAMD64CMPBconst(v *Value) bool {
 			break
 		}
 		m := auxIntToInt32(v_0.AuxInt)
-		if !(0 <= m && int8(m) < n) {
+		if !(0 <= int8(m) && int8(m) < n) {
 			break
 		}
 		v.reset(OpAMD64FlagLT_ULT)
@@ -8243,7 +8243,7 @@ func rewriteValueAMD64_OpAMD64CMPWconst(v *Value) bool {
 		return true
 	}
 	// match: (CMPWconst (ANDLconst _ [m]) [n])
-	// cond: 0 <= m && int16(m) < n
+	// cond: 0 <= int16(m) && int16(m) < n
 	// result: (FlagLT_ULT)
 	for {
 		n := auxIntToInt16(v.AuxInt)
@@ -8251,7 +8251,7 @@ func rewriteValueAMD64_OpAMD64CMPWconst(v *Value) bool {
 			break
 		}
 		m := auxIntToInt32(v_0.AuxInt)
-		if !(0 <= m && int16(m) < n) {
+		if !(0 <= int16(m) && int16(m) < n) {
 			break
 		}
 		v.reset(OpAMD64FlagLT_ULT)
diff --git a/test/fixedbugs/issue41872.go b/test/fixedbugs/issue41872.go
new file mode 100644
index 0000000000..837d61ae0a
--- /dev/null
+++ b/test/fixedbugs/issue41872.go
@@ -0,0 +1,26 @@
+// run
+
+// Copyright 2020 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.
+
+package main
+
+//go:noinline
+func f8(x int32) bool {
+	return byte(x&0xc0) == 64
+}
+
+//go:noinline
+func f16(x int32) bool {
+	return uint16(x&0x8040) == 64
+}
+
+func main() {
+	if !f8(64) {
+		panic("wanted true, got false")
+	}
+	if !f16(64) {
+		panic("wanted true, got false")
+	}
+}