diff --git a/lib/asbind-instance/asbind-instance.js b/lib/asbind-instance/asbind-instance.js
index d09316c..4422792 100644
--- a/lib/asbind-instance/asbind-instance.js
+++ b/lib/asbind-instance/asbind-instance.js
@@ -45,6 +45,7 @@ export default class AsbindInstance {
     this.unboundExports = {};
     this.exports = {};
     this.importObject = {};
+    this.asyncifyStorageSize = 8 * 1024;
   }
 
   getTypeId(typeName) {
@@ -62,6 +63,11 @@ export default class AsbindInstance {
   }
 
   _validate() {
+    this.isAsyncifyModule = Boolean(
+      WebAssembly.Module.exports(this.module).find(
+        ({ name }) => name === "asyncify_start_unwind"
+      )
+    );
     if (
       !WebAssembly.Module.exports(this.module).find(exp => exp.name === "__new")
     ) {
@@ -136,5 +142,11 @@ export default class AsbindInstance {
         descriptor
       );
     }
+
+    if (!this.isAsyncifyModule) {
+      // If this module wasn’t built with Ayncify, we mock
+      // the asyncify state function to return that we are in “normal” mode.
+      this.exports.asyncify_get_state = () => 0;
+    }
   }
 }
diff --git a/lib/asbind-instance/bind-function.js b/lib/asbind-instance/bind-function.js
index e96b347..a5e7208 100644
--- a/lib/asbind-instance/bind-function.js
+++ b/lib/asbind-instance/bind-function.js
@@ -27,6 +27,18 @@ export function bindImportFunction(
   // Create a wrapper function that applies the correct converter function to arguments and
   // return value respectively.
   return function(...args) {
+    if (asbindInstance.exports.asyncify_get_state() === 2 /* Rewinding */) {
+      asbindInstance.loadedModule.exports.asyncify_stop_rewind();
+      asbindInstance.loadedModule.exports.__unpin(
+        asbindInstance.asyncifyState.ptr
+      );
+      return returnValueConverterFunction(
+        asbindInstance,
+        asbindInstance.asyncifyState.value,
+        importedFunctionDescriptor.returnType
+      );
+    }
+
     if (args.length != argumentConverterFunctions.length) {
       throw Error(
         `Expected ${argumentConverterFunctions.length} arguments, got ${args.length}`
@@ -40,11 +52,35 @@ export function bindImportFunction(
       )
     );
     const result = importedFunction(...newArgs);
-    return returnValueConverterFunction(
-      asbindInstance,
-      result,
-      importedFunctionDescriptor.returnType
+    if (!asbindInstance.isAsyncifyModule || !(result instanceof Promise)) {
+      return returnValueConverterFunction(
+        asbindInstance,
+        result,
+        importedFunctionDescriptor.returnType
+      );
+    }
+    asbindInstance.asyncifyState = {
+      ptr: asbindInstance.loadedModule.exports.__new(
+        asbindInstance.asyncifyStorageSize,
+        0
+      )
+    };
+    asbindInstance.loadedModule.exports.__pin(asbindInstance.asyncifyState.ptr);
+    const dv = new DataView(asbindInstance.loadedModule.exports.memory.buffer);
+    dv.setUint32(
+      asbindInstance.asyncifyState.ptr,
+      asbindInstance.asyncifyState.ptr + 8,
+      true
     );
+    dv.setUint32(
+      asbindInstance.asyncifyState.ptr + 4,
+      asbindInstance.asyncifyState.ptr + asbindInstance.asyncifyStorageSize,
+      true
+    );
+    asbindInstance.loadedModule.exports.asyncify_start_unwind(
+      asbindInstance.asyncifyState.ptr
+    );
+    asbindInstance.asyncifyState.promise = result;
   };
 }
 
@@ -78,11 +114,25 @@ export function bindExportFunction(
         exportedFunctionDescriptor.parameters[i]
       )
     );
-    const result = exportedFunction(...newArgs);
-    return returnValueConverterFunction(
-      asbindInstance,
-      result,
-      exportedFunctionDescriptor.returnType
-    );
+    return function f(...args) {
+      const result = exportedFunction(...args);
+      if (asbindInstance.exports.asyncify_get_state() === 0 /* Normal */) {
+        return returnValueConverterFunction(
+          asbindInstance,
+          result,
+          exportedFunctionDescriptor.returnType
+        );
+      }
+      asbindInstance.loadedModule.exports.asyncify_stop_unwind();
+      let localAsyncifyState = asbindInstance.asyncifyState;
+      return localAsyncifyState.promise.then(value => {
+        localAsyncifyState.value = value;
+        asbindInstance.asyncifyState = localAsyncifyState;
+        asbindInstance.loadedModule.exports.asyncify_start_rewind(
+          asbindInstance.asyncifyState.ptr
+        );
+        return f(...args);
+      });
+    }.bind(this)(...newArgs);
   };
 }
diff --git a/test/test-runner.js b/test/test-runner.js
index 7456d41..095d806 100644
--- a/test/test-runner.js
+++ b/test/test-runner.js
@@ -1,5 +1,6 @@
 const { promisify } = require("util");
 const fs = require("fs/promises");
+const path = require("path");
 
 const Express = require("express");
 const Mocha = require("mocha");
@@ -32,7 +33,7 @@ async function compileAllAsc() {
   const transformFile = require.resolve("../dist/transform.cjs.js");
   for (const ascFile of ascFiles) {
     console.log(`Compiling ${ascFile}...`);
-    await asc.main([
+    const params = [
       "--runtime",
       "stub",
       "--exportRuntime",
@@ -41,7 +42,13 @@ async function compileAllAsc() {
       "--binaryFile",
       ascFile.replace(/\.ts$/, ".wasm"),
       ascFile
-    ]);
+    ];
+    try {
+      const configFile = "./" + path.join(path.dirname(ascFile), "config.js");
+      const config = require(configFile);
+      await config?.params?.(params);
+    } catch (e) {}
+    await asc.main(params);
   }
 }
 
diff --git a/test/tests/string-promise/asc.ts b/test/tests/string-promise/asc.ts
new file mode 100644
index 0000000..92a577a
--- /dev/null
+++ b/test/tests/string-promise/asc.ts
@@ -0,0 +1,5 @@
+export function swapAndPad(a: string, b: string): string {
+  return "!" + swappedConcat(a, b) + "!";
+}
+
+declare function swappedConcat(a: string, b: string): string;
diff --git a/test/tests/string-promise/config.js b/test/tests/string-promise/config.js
new file mode 100644
index 0000000..7c95bef
--- /dev/null
+++ b/test/tests/string-promise/config.js
@@ -0,0 +1,5 @@
+module.exports = {
+  params(param) {
+    param.push("--runPasses", "asyncify");
+  }
+};
diff --git a/test/tests/string-promise/test.js b/test/tests/string-promise/test.js
new file mode 100644
index 0000000..4af38cc
--- /dev/null
+++ b/test/tests/string-promise/test.js
@@ -0,0 +1,12 @@
+describe("as-bind", function() {
+  it("should handle strings", async function() {
+    const instance = await AsBind.instantiate(this.rawModule, {
+      asc: {
+        async swappedConcat(a, b) {
+          return b + a;
+        }
+      }
+    });
+    assert((await instance.exports.swapAndPad("a", "b")) === "!ba!");
+  });
+});