diff --git a/lib/wasi/src/state/builder.rs b/lib/wasi/src/state/builder.rs
index 0bd8bd2185d..fd3ab222192 100644
--- a/lib/wasi/src/state/builder.rs
+++ b/lib/wasi/src/state/builder.rs
@@ -438,6 +438,9 @@ impl PreopenDirBuilder {
 
     /// Make this preopened directory appear to the WASI program as `alias`
     pub fn alias(&mut self, alias: &str) -> &mut Self {
+        // We mount at preopened dirs at `/` by default and multiple `/` in a row
+        // are equal to a single `/`.
+        let alias = alias.trim_start_matches(b'/');
         self.alias = Some(alias.to_string());
 
         self
diff --git a/tests/wasi-wast/wasi/snapshot1/mapdir_with_leading_slash.wasm b/tests/wasi-wast/wasi/snapshot1/mapdir_with_leading_slash.wasm
new file mode 100644
index 00000000000..26e68d85722
Binary files /dev/null and b/tests/wasi-wast/wasi/snapshot1/mapdir_with_leading_slash.wasm differ
diff --git a/tests/wasi-wast/wasi/snapshot1/mapdir_with_leading_slash.wast b/tests/wasi-wast/wasi/snapshot1/mapdir_with_leading_slash.wast
new file mode 100644
index 00000000000..945e660f72c
--- /dev/null
+++ b/tests/wasi-wast/wasi/snapshot1/mapdir_with_leading_slash.wast
@@ -0,0 +1,7 @@
+;; This file was generated by https://github.com/wasmerio/wasi-tests
+
+(wasi_test "mapdir_with_leading_slash.wasm"
+  (map_dirs "/hamlet:test_fs/hamlet")
+  (assert_return (i64.const 0))
+  (assert_stdout "File exists? true\nSCENE III. A room in the castle.\n\n    Enter KING CLAUDIUS, ROSENCRANTZ, and GUILDENSTERN \n\nKING CLAUDIUS\n\n    I like him not, nor stands it safe with us\n    To let his madness range. Therefore prepare you;\n    I your commission will forthwith dispatch,\n   \n")
+)
diff --git a/tests/wasi-wast/wasi/tests/mapdir_with_leading_slash.rs b/tests/wasi-wast/wasi/tests/mapdir_with_leading_slash.rs
new file mode 100644
index 00000000000..979af37e3dc
--- /dev/null
+++ b/tests/wasi-wast/wasi/tests/mapdir_with_leading_slash.rs
@@ -0,0 +1,23 @@
+// WASI:
+// mapdir: /hamlet:test_fs/hamlet
+
+use std::fs;
+use std::io::Read;
+use std::path::PathBuf;
+
+fn main() {
+    #[cfg(not(target_os = "wasi"))]
+    let mut base = PathBuf::from("test_fs/hamlet");
+    #[cfg(target_os = "wasi")]
+    let mut base = PathBuf::from("hamlet");
+
+    base.push("act3/scene3.txt");
+
+    println!("File exists? {}", base.exists());
+
+    let mut f = fs::File::open(&base).unwrap();
+    let mut s = String::new();
+    f.read_to_string(&mut s).unwrap();
+
+    println!("{}", s.chars().take(256).collect::<String>());
+}
diff --git a/tests/wasi-wast/wasi/unstable/mapdir_with_leading_slash.wasm b/tests/wasi-wast/wasi/unstable/mapdir_with_leading_slash.wasm
new file mode 100644
index 00000000000..eacc71d81e3
Binary files /dev/null and b/tests/wasi-wast/wasi/unstable/mapdir_with_leading_slash.wasm differ
diff --git a/tests/wasi-wast/wasi/unstable/mapdir_with_leading_slash.wast b/tests/wasi-wast/wasi/unstable/mapdir_with_leading_slash.wast
new file mode 100644
index 00000000000..945e660f72c
--- /dev/null
+++ b/tests/wasi-wast/wasi/unstable/mapdir_with_leading_slash.wast
@@ -0,0 +1,7 @@
+;; This file was generated by https://github.com/wasmerio/wasi-tests
+
+(wasi_test "mapdir_with_leading_slash.wasm"
+  (map_dirs "/hamlet:test_fs/hamlet")
+  (assert_return (i64.const 0))
+  (assert_stdout "File exists? true\nSCENE III. A room in the castle.\n\n    Enter KING CLAUDIUS, ROSENCRANTZ, and GUILDENSTERN \n\nKING CLAUDIUS\n\n    I like him not, nor stands it safe with us\n    To let his madness range. Therefore prepare you;\n    I your commission will forthwith dispatch,\n   \n")
+)