diff --git a/README.md b/README.md
index 9dea351..4bbffda 100644
--- a/README.md
+++ b/README.md
@@ -8,8 +8,8 @@ hash algorithm can be changed.
 
 ### Build Requirements
 Building with NEON support requires CGO enabled and a working C compiler.
-On 32-bit ARM (armv7) the C and C++ implementations are disabled and the
-program always uses pure Go fallbacks.
+The optional C implementations are only built on amd64 and arm64. Other
+architectures, including 32-bit ARM (armv7), always use the pure Go fallbacks.
 
 ## Usage
 
@@ -77,15 +77,15 @@ vectorized code when available. The `t1ha` routines include tuned
 implementations with optional AES and NEON support and fall back to
 portable code on other CPUs. No official armv7 assembly is provided.
 Wyhash and its successor `rapidhash` can use optional C wrappers
-compiled with `-msse2` on Intel or `-mfpu=neon` on ARM64. When CGO is
-enabled and the CPU supports these features, the program calls the C
-implementation for additional speed. Otherwise the pure Go fallback is
-used automatically. On 32-bit ARM (armv7) these C paths are disabled and
-the pure Go implementations are always used.
+compiled with `-msse2` on Intel or `-mfpu=neon` on ARM64. These wrappers
+are only built on amd64 and arm64. When CGO is enabled and the CPU
+supports the required features, the program calls the C implementation
+for additional speed. Otherwise the pure Go fallback is used
+automatically.
 When NEON is detected the program also uses the official BLAKE3 C
 implementation via CGO for additional performance. The C implementation
-is not built on armv7 where the pure Go version is used. A working C
-toolchain is required in this case.
+is only built on amd64 and arm64; other platforms use the pure Go
+version. A working C toolchain is required in this case.
 On older CPUs without these capabilities it transparently falls back to Go's
 standard implementations. This happens automatically at startup and
 works across different architectures.
diff --git a/blake3c/blake3c.go b/blake3c/blake3c.go
index c546e5c..9c45799 100644
--- a/blake3c/blake3c.go
+++ b/blake3c/blake3c.go
@@ -1,4 +1,4 @@
-//go:build cgo && !arm
+//go:build cgo && (amd64 || arm64)
 
 package blake3c
 
diff --git a/rapidhashc/rapidhashc.go b/rapidhashc/rapidhashc.go
index 2498f98..8344063 100644
--- a/rapidhashc/rapidhashc.go
+++ b/rapidhashc/rapidhashc.go
@@ -1,4 +1,4 @@
-//go:build cgo && !arm
+//go:build cgo && (amd64 || arm64)
 
 package rapidhashc
 
diff --git a/t1ha/t1ha.go b/t1ha/t1ha.go
index 8d6eda8..3edfae1 100644
--- a/t1ha/t1ha.go
+++ b/t1ha/t1ha.go
@@ -1,4 +1,4 @@
-//go:build cgo && !arm
+//go:build cgo && (amd64 || arm64)
 
 package t1ha
 
diff --git a/wyhashc/wyhashc.go b/wyhashc/wyhashc.go
index f0fb259..d20b8d0 100644
--- a/wyhashc/wyhashc.go
+++ b/wyhashc/wyhashc.go
@@ -1,4 +1,4 @@
-//go:build cgo && !arm
+//go:build cgo && (amd64 || arm64)
 
 package wyhashc