diff --git a/src/crypto/crypto_timing.cc b/src/crypto/crypto_timing.cc
index 103a620d63726f..ebd5aecce255de 100644
--- a/src/crypto/crypto_timing.cc
+++ b/src/crypto/crypto_timing.cc
@@ -57,7 +57,8 @@ bool FastTimingSafeEqual(Local<Value> receiver,
   uint8_t* data_b;
   if (a.length() != b.length() || !a.getStorageIfAligned(&data_a) ||
       !b.getStorageIfAligned(&data_b)) {
-    options.fallback = true;
+    Environment* env = Environment::GetCurrent(options.isolate);
+    THROW_ERR_CRYPTO_TIMING_SAFE_EQUAL_LENGTH(env);
     return false;
   }
 
diff --git a/src/histogram.cc b/src/histogram.cc
index 4dbdea9be57214..4aacaa2a5d1253 100644
--- a/src/histogram.cc
+++ b/src/histogram.cc
@@ -193,7 +193,8 @@ void HistogramBase::FastRecord(Local<Value> receiver,
                                const int64_t value,
                                FastApiCallbackOptions& options) {
   if (value < 1) {
-    options.fallback = true;
+    Environment* env = Environment::GetCurrent(options.isolate);
+    THROW_ERR_OUT_OF_RANGE(env, "value is out of range");
     return;
   }
   HistogramBase* histogram;
diff --git a/src/node_wasi.cc b/src/node_wasi.cc
index ad1da44a01f437..b77a1f57854261 100644
--- a/src/node_wasi.cc
+++ b/src/node_wasi.cc
@@ -248,17 +248,17 @@ R WASI::WasiFunction<FT, F, R, Args...>::FastCallback(
   WASI* wasi = reinterpret_cast<WASI*>(BaseObject::FromJSObject(receiver));
   if (UNLIKELY(wasi == nullptr)) return EinvalError<R>();
 
-  if (UNLIKELY(options.wasm_memory == nullptr || wasi->memory_.IsEmpty())) {
-    // fallback to slow path which to throw an error about missing memory.
-    options.fallback = true;
-    return EinvalError<R>();
+  v8::Isolate* isolate = receiver->GetIsolate();
+  if (wasi->memory_.IsEmpty()) {
+    THROW_ERR_WASI_NOT_STARTED(isolate);
+    return;
   }
-  uint8_t* memory = nullptr;
-  CHECK(LIKELY(options.wasm_memory->getStorageIfAligned(&memory)));
+  Local<ArrayBuffer> ab = wasi->memory_.Get(isolate)->Buffer();
+  size_t mem_size = ab->ByteLength();
+  char* mem_data = static_cast<char*>(ab->Data());
+  CHECK_NOT_NULL(mem_data);
 
-  return F(*wasi,
-           {reinterpret_cast<char*>(memory), options.wasm_memory->length()},
-           args...);
+  return F(*wasi, {mem_data, mem_size}, args...);
 }
 
 namespace {