diff --git a/base/include/android-base/unique_fd.h b/base/include/android-base/unique_fd.h
index 83213e9..3fa3bea 100644
--- a/base/include/android-base/unique_fd.h
+++ b/base/include/android-base/unique_fd.h
@@ -105,6 +105,9 @@
   int get() const { return fd_; }
   operator int() const { return get(); }  // NOLINT
 
+  // Catch bogus error checks (i.e.: "!fd" instead of "fd != -1").
+  bool operator!() const = delete;
+
   int release() __attribute__((warn_unused_result)) {
     tag(fd_, this, nullptr);
     int ret = fd_;
diff --git a/init/service.cpp b/init/service.cpp
index 6d08cb1..f5c13b9 100644
--- a/init/service.cpp
+++ b/init/service.cpp
@@ -177,7 +177,7 @@
 Result<Success> Service::EnterNamespaces() const {
     for (const auto& [nstype, path] : namespaces_to_enter_) {
         auto fd = unique_fd{open(path.c_str(), O_RDONLY | O_CLOEXEC)};
-        if (!fd) {
+        if (fd == -1) {
             return ErrnoError() << "Could not open namespace at " << path;
         }
         if (setns(fd, nstype) == -1) {