diff --git a/compileopts/config.go b/compileopts/config.go
index 7afdded3..b22db15d 100644
--- a/compileopts/config.go
+++ b/compileopts/config.go
@@ -544,6 +544,8 @@ func (c *Config) Emulator(format, binary string) ([]string, error) {
 	var emulator []string
 	for _, s := range parts {
 		s = strings.ReplaceAll(s, "{root}", goenv.Get("TINYGOROOT"))
+		// Allow replacement of what's usually /tmp except notably Windows.
+		s = strings.ReplaceAll(s, "{tmpDir}", os.TempDir())
 		s = strings.ReplaceAll(s, "{"+format+"}", binary)
 		emulator = append(emulator, s)
 	}
diff --git a/main.go b/main.go
index 4e24a9ab..44eacb2c 100644
--- a/main.go
+++ b/main.go
@@ -293,17 +293,6 @@ func Test(pkgName string, stdout, stderr io.Writer, options *compileopts.Options
 				args = append(args, "--dir="+d)
 			}
 
-			// Some tests create temp directories using os.MkdirTemp or via
-			// t.TempDir(). Create a writeable directory and map it to the
-			// default tempDir environment variable: TMPDIR.
-			tmpdir, err := os.MkdirTemp("", "tinygotmp")
-			if err != nil {
-				return fmt.Errorf("failed to create temporary directory: %w", err)
-			}
-			args = append(args, "--dir="+tmpdir, "--env=TMPDIR="+tmpdir)
-			// TODO: add option to not delete temp dir for debugging?
-			defer os.RemoveAll(tmpdir)
-
 			// The below re-organizes the arguments so that the current
 			// directory is added last.
 			args = append(args, cmd.Args[1:]...)
diff --git a/targets/wasi.json b/targets/wasi.json
index 6cec6be4..c6b418fe 100644
--- a/targets/wasi.json
+++ b/targets/wasi.json
@@ -21,6 +21,6 @@
 	"extra-files": [
 		"src/runtime/asm_tinygowasm.S"
 	],
-	"emulator":      "wasmtime {}",
+	"emulator":      "wasmtime --mapdir=/tmp::{tmpDir} {}",
 	"wasm-abi":      "generic"
 }