diff --git a/src/api/environment.cc b/src/api/environment.cc
index a87f591e4edf57..70228b77d8860b 100644
--- a/src/api/environment.cc
+++ b/src/api/environment.cc
@@ -139,7 +139,11 @@ void DebuggingArrayBufferAllocator::UnregisterPointerInternal(void* data,
   if (data == nullptr) return;
   auto it = allocations_.find(data);
   CHECK_NE(it, allocations_.end());
-  CHECK_EQ(it->second, size);
+  if (size > 0) {
+    // We allow allocations with size 1 for 0-length buffers to avoid having
+    // to deal with nullptr values.
+    CHECK_EQ(it->second, size);
+  }
   allocations_.erase(it);
 }
 
diff --git a/src/node_buffer.cc b/src/node_buffer.cc
index 19d2de96b1c057..58175a8fd5f615 100644
--- a/src/node_buffer.cc
+++ b/src/node_buffer.cc
@@ -420,7 +420,7 @@ MaybeLocal<Object> New(Environment* env,
   }
 
   if (uses_malloc) {
-    if (env->isolate_data()->uses_node_allocator()) {
+    if (!env->isolate_data()->uses_node_allocator()) {
       // We don't know for sure that the allocator is malloc()-based, so we need
       // to fall back to the FreeCallback variant.
       auto free_callback = [](char* data, void* hint) { free(data); };