diff --git a/include/proxy-wasm/context.h b/include/proxy-wasm/context.h
index c373cf32..2487e30a 100644
--- a/include/proxy-wasm/context.h
+++ b/include/proxy-wasm/context.h
@@ -245,6 +245,19 @@ class ContextBase : public RootInterface,
 #else
     unimplemented();
     return 0;
+#endif
+  }
+  uint64_t getMonotonicTimeNanoseconds() override {
+#if !defined(_MSC_VER)
+    struct timespec tpe;
+    clock_gettime(CLOCK_MONOTONIC, &tpe);
+    uint64_t t = tpe.tv_sec;
+    t *= 1000000000;
+    t += tpe.tv_nsec;
+    return t;
+#else
+    unimplemented();
+    return 0;
 #endif
   }
   std::string_view getConfiguration() override {
diff --git a/include/proxy-wasm/context_interface.h b/include/proxy-wasm/context_interface.h
index 1a6f738d..841dd0e1 100644
--- a/include/proxy-wasm/context_interface.h
+++ b/include/proxy-wasm/context_interface.h
@@ -557,6 +557,9 @@ struct GeneralInterface {
   // Provides the current time in nanoseconds since the Unix epoch.
   virtual uint64_t getCurrentTimeNanoseconds() = 0;
 
+  // Provides the monotonic time in nanoseconds.
+  virtual uint64_t getMonotonicTimeNanoseconds() = 0;
+
   // Returns plugin configuration.
   virtual std::string_view getConfiguration() = 0;
 
diff --git a/src/exports.cc b/src/exports.cc
index 97bbab06..9a6431ce 100644
--- a/src/exports.cc
+++ b/src/exports.cc
@@ -833,12 +833,19 @@ Word wasi_unstable_args_sizes_get(void *raw_context, Word argc_ptr, Word argv_bu
 Word wasi_unstable_clock_time_get(void *raw_context, Word clock_id, uint64_t precision,
                                   Word result_time_uint64_ptr) {
 
-  if (clock_id != 0 /* realtime */) {
+  uint64_t result = 0;
+  auto context = WASM_CONTEXT(raw_context);
+  switch (clock_id) {
+  case 0 /* realtime */:
+    result = context->getCurrentTimeNanoseconds();
+    break;
+  case 1 /* monotonic */:
+    result = context->getMonotonicTimeNanoseconds();
+    break;
+  default:
+    // process_cputime_id and thread_cputime_id are not supported yet.
     return 58; // __WASI_ENOTSUP
   }
-
-  auto context = WASM_CONTEXT(raw_context);
-  uint64_t result = context->getCurrentTimeNanoseconds();
   if (!context->wasm()->setDatatype(result_time_uint64_ptr, result)) {
     return 21; // __WASI_EFAULT
   }
diff --git a/test/BUILD b/test/BUILD
index 0fad5ceb..60ff362a 100644
--- a/test/BUILD
+++ b/test/BUILD
@@ -37,6 +37,7 @@ cc_test(
     srcs = ["exports_test.cc"],
     copts = COPTS,
     data = [
+        "//test/test_data:clock.wasm",
         "//test/test_data:env.wasm",
     ],
     linkopts = LINKOPTS,
diff --git a/test/exports_test.cc b/test/exports_test.cc
index 74e23c08..c35ea02d 100644
--- a/test/exports_test.cc
+++ b/test/exports_test.cc
@@ -91,5 +91,28 @@ TEST_P(TestVM, WithoutEnvironment) {
   EXPECT_EQ(context.log_msg(), "");
 }
 
+TEST_P(TestVM, Clock) {
+  initialize("clock.wasm");
+  auto wasm_base = WasmBase(std::move(vm_), "vm_id", "", "", {}, {});
+  ASSERT_TRUE(wasm_base.wasm_vm()->load(source_, false));
+
+  TestContext context(&wasm_base);
+  current_context_ = &context;
+
+  wasm_base.registerCallbacks();
+
+  ASSERT_TRUE(wasm_base.wasm_vm()->link(""));
+
+  WasmCallVoid<0> run;
+  wasm_base.wasm_vm()->getFunction("run", &run);
+  ASSERT_TRUE(run);
+  run(current_context_);
+
+  // Check logs.
+  auto msg = context.log_msg();
+  EXPECT_NE(std::string::npos, msg.find("monotonic: ")) << msg;
+  EXPECT_NE(std::string::npos, msg.find("realtime: ")) << msg;
+}
+
 } // namespace
 } // namespace proxy_wasm
diff --git a/test/test_data/BUILD b/test/test_data/BUILD
index 715ed92e..3d99c103 100644
--- a/test/test_data/BUILD
+++ b/test/test_data/BUILD
@@ -22,3 +22,9 @@ wasm_rust_binary(
     srcs = ["env.rs"],
     wasi = True,
 )
+
+wasm_rust_binary(
+    name = "clock.wasm",
+    srcs = ["clock.rs"],
+    wasi = True,
+)
diff --git a/test/test_data/clock.rs b/test/test_data/clock.rs
new file mode 100644
index 00000000..480a2b1b
--- /dev/null
+++ b/test/test_data/clock.rs
@@ -0,0 +1,21 @@
+// Copyright 2021 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+use std::time::{Instant, SystemTime};
+
+#[no_mangle]
+pub extern "C" fn run() {
+    println!("monotonic: {:?}", Instant::now());
+    println!("realtime: {:?}", SystemTime::now());
+}