diff --git a/include/fmt/format.h b/include/fmt/format.h
index c19a6604..a09b3e84 100644
--- a/include/fmt/format.h
+++ b/include/fmt/format.h
@@ -700,7 +700,7 @@ class basic_memory_buffer : public internal::buffer<T> {
 template <typename T, std::size_t SIZE, typename Allocator>
 void basic_memory_buffer<T, SIZE, Allocator>::grow(std::size_t size) {
 #ifdef FMT_FUZZ
-  if (size > 1000) throw std::runtime_error("fuzz mode - won't grow that much");
+  if (size > 5000) throw std::runtime_error("fuzz mode - won't grow that much");
 #endif
   std::size_t old_capacity = this->capacity();
   std::size_t new_capacity = old_capacity + old_capacity / 2;
@@ -1138,7 +1138,7 @@ template <typename Char> class float_writer {
           return it;
         }
 #ifdef FMT_FUZZ
-        if (num_zeros > 1000)
+        if (num_zeros > 5000)
           throw std::runtime_error("fuzz mode - avoiding excessive cpu use");
 #endif
         it = std::fill_n(it, num_zeros, static_cast<Char>('0'));