diff --git a/iguana/detail/charconv.h b/iguana/detail/charconv.h
index c17e52e6..16b34be7 100644
--- a/iguana/detail/charconv.h
+++ b/iguana/detail/charconv.h
@@ -18,25 +18,23 @@ namespace detail {
 template <bool check_number = true, typename U>
 std::pair<const char *, std::errc> from_chars(const char *first,
                                               const char *last, U &value) {
-#define CHECK_NUM                     \
-  if (p != last || ec != std::errc{}) \
-    IGUANA_UNLIKELY { throw std::runtime_error("Failed to parse number"); }
   using T = std::decay_t<U>;
   if constexpr (std::is_floating_point_v<T>) {
     auto [p, ec] = fast_float::from_chars(first, last, value);
     if constexpr (check_number) {
-      CHECK_NUM
+      if (p != last || ec != std::errc{})
+        IGUANA_UNLIKELY { throw std::runtime_error("Failed to parse number"); }
     }
     return {p, ec};
   }
   else {
     auto [p, ec] = std::from_chars(first, last, value);
     if constexpr (check_number) {
-      CHECK_NUM
+      if (p != last || ec != std::errc{})
+        IGUANA_UNLIKELY { throw std::runtime_error("Failed to parse number"); }
     }
     return {p, ec};
   }
-#undef CHECK_NUM
 }
 
 // not support uint8 for now
diff --git a/iguana/json_reader.hpp b/iguana/json_reader.hpp
index d99ef08a..1dcd9a58 100644
--- a/iguana/json_reader.hpp
+++ b/iguana/json_reader.hpp
@@ -69,10 +69,7 @@ IGUANA_INLINE void from_json_impl(U &value, It &&it, It &&end) {
       IGUANA_UNLIKELY { throw std::runtime_error("Failed to parse number"); }
     const auto start = &*it;
     auto [p, ec] = detail::from_chars<false>(start, start + size, value);
-    // TODO: improve by static array
-    if (ec != std::errc{} ||
-        !(*p == '}' || *p == ']' || *p == ',' || *p == ' ' || *p == '\0' ||
-          *p == '"' || *p == '\n'))
+    if (ec != std::errc{} || !can_follow_number(*p))
       IGUANA_UNLIKELY { throw std::runtime_error("Failed to parse number"); }
     it += (p - &*it);
   }
diff --git a/iguana/json_util.hpp b/iguana/json_util.hpp
index 1b0f5db3..f1bf3a33 100644
--- a/iguana/json_util.hpp
+++ b/iguana/json_util.hpp
@@ -211,4 +211,28 @@ IGUANA_INLINE bool is_numeric(char c) noexcept {
   return static_cast<bool>(is_num[static_cast<unsigned int>(c)]);
 }
 
+// '\t' '\r' '\n'  '"' '}' ']' ',' ' '  '\0'
+IGUANA_INLINE bool can_follow_number(char c) noexcept {
+  static constexpr int can_follow_num[256] = {
+      //  0  1  2  3  4  5  6  7  8  9  A  B  C  D  E  F
+      1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 0, 0,  // 0
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,  // 1
+      1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0,  // 2
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,  // 3
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,  // 4
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0,  // 5
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,  // 6
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0,  // 7
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,  // 8
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,  // 9
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,  // A
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,  // B
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,  // C
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,  // D
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,  // E
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0   // F
+  };
+  return static_cast<bool>(can_follow_num[static_cast<unsigned int>(c)]);
+}
+
 }  // namespace iguana