diff --git a/test/scan-test.cc b/test/scan-test.cc
index 29387a06..e3efba7b 100644
--- a/test/scan-test.cc
+++ b/test/scan-test.cc
@@ -10,27 +10,18 @@
 
 #include "fmt/format.h"
 #include "gmock.h"
+#include "gtest-extra.h"
 
-namespace fmt {
+FMT_BEGIN_NAMESPACE
+namespace internal {
 
 struct scan_arg {
-  int& value;
+  int* value;
   // TODO: more types
 };
 
-struct scan_args {
-  int size;
-  const scan_arg* data;
-
-  template <size_t N>
-  scan_args(const std::array<scan_arg, N>& store)
-      : size(N), data(store.data()) {
-    static_assert(N < INT_MAX, "too many arguments");
-  }
-};
-
 template <typename Handler>
-void parse_scan_format(string_view format_str, Handler& handler) {
+void parse_scan_format(string_view format_str, Handler&& handler) {
   const char* p = format_str.data();
   const char* end = p + format_str.size();
   while (p != end) {
@@ -40,48 +31,70 @@ void parse_scan_format(string_view format_str, Handler& handler) {
     handler.on_arg();
   }
 }
+}  // namespace internal
+
+struct scan_args {
+  int size;
+  const internal::scan_arg* data;
+
+  template <size_t N>
+  scan_args(const std::array<internal::scan_arg, N>& store)
+      : size(N), data(store.data()) {
+    static_assert(N < INT_MAX, "too many arguments");
+  }
+};
+
+namespace internal {
+struct scan_handler {
+  const char* begin;
+  const char* end;
+  scan_args args;
+  int next_arg_id;
+
+  scan_handler(string_view input, scan_args args)
+      : begin(input.data()),
+        end(begin + input.size()),
+        args(args),
+        next_arg_id(0) {}
+
+  void on_arg() {
+    int value = 0;
+    while (begin != end) {
+      char c = *begin++;
+      if (c < '0' || c > '9') throw format_error("invalid input");
+      value = value * 10 + (c - '0');
+    }
+    if (next_arg_id >= args.size)
+      throw format_error("argument index out of range");
+    *args.data[0].value = value;
+  }
+};
+}  // namespace internal
 
 void vscan(string_view input, string_view format_str, scan_args args) {
-  struct handler {
-    const char* begin;
-    const char* end;
-    scan_args args;
-    int next_arg_id;
-
-    handler(string_view input, scan_args args)
-        : begin(input.data()),
-          end(begin + input.size()),
-          args(args),
-          next_arg_id(0) {}
-
-    void on_arg() {
-      int value = 0;
-      while (begin != end) {
-        char c = *begin++;
-        if (c < '0' || c > '9') throw format_error("invalid input");
-        value = value * 10 + (c - '0');
-      }
-      if (next_arg_id >= args.size)
-        throw format_error("argument index out of range");
-      args.data[0].value = value;
-    }
-  } h(input, args);
-  parse_scan_format(format_str, h);
+  internal::parse_scan_format(format_str, internal::scan_handler(input, args));
 }
 
 template <typename... Args>
-std::array<scan_arg, sizeof...(Args)> make_scan_args(Args&... args) {
-  return {args...};
+std::array<internal::scan_arg, sizeof...(Args)> make_scan_args(Args&... args) {
+  return std::array<internal::scan_arg, sizeof...(Args)>{&args...};
 }
 
 template <typename... Args>
 void scan(string_view input, string_view format_str, Args&... args) {
   vscan(input, format_str, make_scan_args(args...));
 }
-}  // namespace fmt
+FMT_END_NAMESPACE
 
 TEST(ScanTest, ReadInt) {
   int n = 0;
   fmt::scan("42", "{}", n);
   EXPECT_EQ(n, 42);
 }
+
+TEST(ScanTest, InvalidFormat) {
+  EXPECT_THROW_MSG(fmt::scan("", "{}"), fmt::format_error,
+                   "argument index out of range");
+  EXPECT_THROW_MSG(fmt::scan("", "{"), fmt::format_error,
+                   "invalid format string");
+}