diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 2ec4b3e..17cc733 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -24,7 +24,9 @@ jobs:
       - name: Build
         run: go build -v ./...
       - name: Test
-        run: make test
+        run: |
+          make test
+          make test-wasm
       - name: Checks
         run: |
           make checks
diff --git a/Makefile b/Makefile
index 2728016..365770b 100644
--- a/Makefile
+++ b/Makefile
@@ -20,9 +20,13 @@ test: tools/ts
 	go tool covdata textfmt -i=./coverage/covdata -o ./coverage/covprofile
 	go tool cover -html=./coverage/covprofile -o ./coverage/coverage.html
 
-just_test:
+just-test:
 	go test -v -vet=all -timeout 15m ./...
 
+test-wasm:
+# https://go.dev/wiki/WebAssembly#executing-webassembly-with-nodejs
+	PATH="$$PATH:$$(go env GOROOT)/lib/wasm" GOOS=js GOARCH=wasm go test -timeout 15m ./...
+
 .PHONY: short-test
 short-test:
 	go test -v -short ./...
diff --git a/conncheck_test.go b/conncheck_test.go
index 3576f13..f450cc9 100644
--- a/conncheck_test.go
+++ b/conncheck_test.go
@@ -9,6 +9,7 @@ import (
 	"errors"
 	"fmt"
 	"net"
+	"runtime"
 	"syscall"
 	"testing"
 	"time"
@@ -19,6 +20,9 @@ import (
 )
 
 func TestDo(t *testing.T) {
+	if runtime.GOOS != "windows" && !IsUnix {
+		t.Skip("not supported on this platform")
+	}
 
 	t.Run("plain", func(t *testing.T) {
 		testSocketConn(t, nil)
diff --git a/flags_non_aix_unix.go b/flags_non_aix_unix.go
index a6431af..deccd66 100644
--- a/flags_non_aix_unix.go
+++ b/flags_non_aix_unix.go
@@ -1,4 +1,4 @@
-//go:build !windows && !aix
+//go:build unix && !aix
 
 package conncheck
 
diff --git a/ostype_generic_test.go b/ostype_generic_test.go
new file mode 100644
index 0000000..fff2340
--- /dev/null
+++ b/ostype_generic_test.go
@@ -0,0 +1,5 @@
+//go:build !unix
+
+package conncheck_test
+
+const IsUnix = false
diff --git a/ostype_unix_test.go b/ostype_unix_test.go
new file mode 100644
index 0000000..26e1d37
--- /dev/null
+++ b/ostype_unix_test.go
@@ -0,0 +1,5 @@
+//go:build unix
+
+package conncheck_test
+
+const IsUnix = true
diff --git a/peek_generic.go b/peek_generic.go
new file mode 100644
index 0000000..4bf1b59
--- /dev/null
+++ b/peek_generic.go
@@ -0,0 +1,9 @@
+//go:build !windows && !unix
+
+package conncheck
+
+import "syscall"
+
+func tryPeek(rawConn syscall.RawConn) Status {
+	return StatusUnknown
+}
diff --git a/peek_unix.go b/peek_unix.go
index e38b547..71bf3c6 100644
--- a/peek_unix.go
+++ b/peek_unix.go
@@ -1,4 +1,4 @@
-//go:build !windows
+//go:build unix
 
 package conncheck