diff --git a/src/cmd/internal/notsha256/sha256block_386.s b/src/cmd/internal/notsha256/sha256block_386.s
index 086a0ab25c..f2ba7d7a9b 100644
--- a/src/cmd/internal/notsha256/sha256block_386.s
+++ b/src/cmd/internal/notsha256/sha256block_386.s
@@ -2,6 +2,9 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build !purego
+// +build !purego
+
 // SHA256 block routine. See sha256block.go for Go equivalent.
 //
 // The algorithm is detailed in FIPS 180-4:
diff --git a/src/cmd/internal/notsha256/sha256block_amd64.go b/src/cmd/internal/notsha256/sha256block_amd64.go
index 676c4f70d9..27b84a86b1 100644
--- a/src/cmd/internal/notsha256/sha256block_amd64.go
+++ b/src/cmd/internal/notsha256/sha256block_amd64.go
@@ -2,6 +2,9 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build !purego
+// +build !purego
+
 package notsha256
 
 var useAVX2 = false
diff --git a/src/cmd/internal/notsha256/sha256block_amd64.s b/src/cmd/internal/notsha256/sha256block_amd64.s
index b2ae7c5fc9..36ea74451d 100644
--- a/src/cmd/internal/notsha256/sha256block_amd64.s
+++ b/src/cmd/internal/notsha256/sha256block_amd64.s
@@ -2,6 +2,9 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build !purego
+// +build !purego
+
 #include "textflag.h"
 
 // SHA256 block routine. See sha256block.go for Go equivalent.
diff --git a/src/cmd/internal/notsha256/sha256block_decl.go b/src/cmd/internal/notsha256/sha256block_decl.go
index 5a822ee479..631f1a4a1b 100644
--- a/src/cmd/internal/notsha256/sha256block_decl.go
+++ b/src/cmd/internal/notsha256/sha256block_decl.go
@@ -2,7 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build 386 || amd64 || ppc64le || ppc64
+//go:build !purego && (386 || amd64 || ppc64le || ppc64)
+// +build !purego
 // +build 386 amd64 ppc64le ppc64
 
 package notsha256
diff --git a/src/cmd/internal/notsha256/sha256block_generic.go b/src/cmd/internal/notsha256/sha256block_generic.go
index 20ae841383..2664722bc2 100644
--- a/src/cmd/internal/notsha256/sha256block_generic.go
+++ b/src/cmd/internal/notsha256/sha256block_generic.go
@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build !amd64 && !386 && !ppc64le && !ppc64
-// +build !amd64,!386,!ppc64le,!ppc64
+//go:build purego || (!amd64 && !386 && !ppc64le && !ppc64)
+// +build purego !amd64,!386,!ppc64le,!ppc64
 
 package notsha256
 
diff --git a/src/cmd/internal/notsha256/sha256block_ppc64x.s b/src/cmd/internal/notsha256/sha256block_ppc64x.s
index 6e0f1d6133..e907d3b71b 100644
--- a/src/cmd/internal/notsha256/sha256block_ppc64x.s
+++ b/src/cmd/internal/notsha256/sha256block_ppc64x.s
@@ -8,7 +8,8 @@
 // bootstrap toolchain.
 //
 
-//go:build ppc64 || ppc64le
+//go:build !purego && (ppc64 || ppc64le)
+// +build !purego
 // +build ppc64 ppc64le
 
 // Based on CRYPTOGAMS code with the following comment: