diff --git a/include/fmt/format-inl.h b/include/fmt/format-inl.h
index 945cb912..331c034a 100644
--- a/include/fmt/format-inl.h
+++ b/include/fmt/format-inl.h
@@ -30,6 +30,14 @@
 #  define FMT_FUNC
 #endif
 
+#if defined(FMT_USE_FULL_CACHE_DRAGONBOX)
+// Use the provided definition.
+#elif defined(__OPTIMIZE_SIZE__)
+#  define FMT_USE_FULL_CACHE_DRAGONBOX 0
+#else
+#  define FMT_USE_FULL_CACHE_DRAGONBOX 1
+#endif
+
 FMT_BEGIN_NAMESPACE
 
 #ifndef FMT_CUSTOM_ASSERT_FAIL
diff --git a/include/fmt/format.h b/include/fmt/format.h
index 039a7a37..2e57c71e 100644
--- a/include/fmt/format.h
+++ b/include/fmt/format.h
@@ -736,10 +736,6 @@ using fast_float_t = conditional_t<sizeof(T) == sizeof(double), double, float>;
 template <typename T>
 using is_double_double = bool_constant<std::numeric_limits<T>::digits == 106>;
 
-#ifndef FMT_USE_FULL_CACHE_DRAGONBOX
-#  define FMT_USE_FULL_CACHE_DRAGONBOX 0
-#endif
-
 // An allocator that uses malloc/free to allow removing dependency on the C++
 // standard libary runtime. std::decay is used for back_inserter to be found by
 // ADL when applied to memory_buffer.