diff --git a/psicash.cpp b/psicash.cpp
index 794a726..05d6a2b 100644
--- a/psicash.cpp
+++ b/psicash.cpp
@@ -80,7 +80,11 @@ constexpr int HTTPResult::CRITICAL_ERROR;
 constexpr int HTTPResult::RECOVERABLE_ERROR;
 
 PsiCash::PsiCash()
-        : server_port_(0), make_http_request_fn_(nullptr) {
+        : test_(false),
+          initialized_(false),
+          server_port_(0),
+          user_data_(std::make_unique<UserData>()),
+          make_http_request_fn_(nullptr) {
 }
 
 PsiCash::~PsiCash() {
@@ -111,9 +115,16 @@ Error PsiCash::Init(const string& user_agent, const string& file_store_root,
     // May still be null.
     make_http_request_fn_ = std::move(make_http_request_fn);
 
-    user_data_ = std::make_unique<UserData>();
-    auto err = user_data_->Init(file_store_root, test);
-    return PassError(err);
+    if (auto err = user_data_->Init(file_store_root, test)) {
+        return PassError(err);
+    }
+
+    initialized_ = true;
+    return error::nullerr;
+}
+
+bool PsiCash::Initialized() const {
+    return initialized_;
 }
 
 Error PsiCash::Reset(const string& file_store_root, bool test) {
@@ -598,6 +609,10 @@ Result<Status> PsiCash::RefreshState(
      6. If there are still no valid tokens, then things are horribly wrong. Return error.
     */
 
+    if (!initialized_) {
+        return MakeCriticalError("PsiCash is uninitialized");
+    }
+
     auto auth_tokens = user_data_->GetAuthTokens();
     if (auth_tokens.empty()) {
         // No tokens.
@@ -728,8 +743,9 @@ Result<Status> PsiCash::RefreshState(
         return RefreshState(purchase_classes, true);
     } else if (result->code == kHTTPStatusUnauthorized) {
         // This can only happen if the tokens we sent didn't all belong to same user.
-        // This really should never happen.
-        user_data_->Clear();
+        // This really should never happen. We're not checking the return value, as there
+        // isn't a sane response to a failure at this point.
+        (void)user_data_->Clear();
         return Status::InvalidTokens;
     } else if (IsServerError(result->code)) {
         return Status::ServerError;
@@ -743,6 +759,10 @@ Result<PsiCash::NewExpiringPurchaseResponse> PsiCash::NewExpiringPurchase(
         const string& transaction_class,
         const string& distinguisher,
         const int64_t expected_price) {
+    if (!initialized_) {
+        return MakeCriticalError("PsiCash is uninitialized");
+    }
+
     auto result = MakeHTTPRequestWithRetry(
             kMethodPOST,
             "/transaction",
diff --git a/psicash.hpp b/psicash.hpp
index a0112ad..6a674fc 100644
--- a/psicash.hpp
+++ b/psicash.hpp
@@ -172,6 +172,8 @@ class PsiCash {
     /// filesystem).
     /// If `test` is true, then the test server will be used, and other testing interfaces
     /// will be available. Should only be used for testing.
+    /// When uninitialized, data accessors will return zero values, and operations (e.g.,
+    /// RefreshState and NewExpiringPurchase) will return errors.
     error::Error Init(const std::string& user_agent, const std::string& file_store_root,
                       MakeHTTPRequestFn make_http_request_fn, bool test=false);
 
@@ -179,6 +181,9 @@ class PsiCash {
     /// Returns an error if the reset failed, likely indicating a filesystem problem.
     error::Error Reset(const std::string& file_store_root, bool test=false);
 
+    /// Returns true if the library has been successfully initialized (i.e., Init called).
+    bool Initialized() const;
+
     /// Can be used for updating the HTTP requester function pointer.
     void SetHTTPRequestFn(MakeHTTPRequestFn make_http_request_fn);
 
@@ -380,6 +385,7 @@ class PsiCash {
 
 protected:
     bool test_;
+    bool initialized_;
     std::string user_agent_;
     std::string server_scheme_;
     std::string server_hostname_;
diff --git a/psicash_test.cpp b/psicash_test.cpp
index b72fe95..87df3c3 100644
--- a/psicash_test.cpp
+++ b/psicash_test.cpp
@@ -156,6 +156,33 @@ TEST_F(TestPsiCash, InitFail) {
     }
 }
 
+TEST_F(TestPsiCash, UninitializedBehaviour) {
+    {
+        // No Init
+        PsiCashTester pc;
+        ASSERT_FALSE(pc.Initialized());
+
+        ASSERT_EQ(pc.Balance(), 0);
+
+        auto res = pc.RefreshState({"speed-boost"});
+        ASSERT_FALSE(res);
+    }
+    {
+        // Failed Init
+        auto bad_dir = GetTempDir() + "/a/b/c/d/f/g";
+        PsiCashTester pc;
+        auto err = pc.Init(user_agent_, bad_dir.c_str(), nullptr, true);
+        ASSERT_TRUE(err) << bad_dir;
+
+        ASSERT_FALSE(pc.Initialized());
+
+        ASSERT_EQ(pc.Balance(), 0);
+
+        auto res = pc.RefreshState({"speed-boost"});
+        ASSERT_FALSE(res);
+    }
+}
+
 TEST_F(TestPsiCash, Clear) {
     int64_t want_balance = 123;
     auto temp_dir = GetTempDir();