diff --git a/include/fmt/core.h b/include/fmt/core.h
index 9f030e38..2e1ae4b6 100644
--- a/include/fmt/core.h
+++ b/include/fmt/core.h
@@ -910,7 +910,8 @@ template <typename Char> struct named_arg_info {
 template <typename T, typename Char, size_t NUM_ARGS, size_t NUM_NAMED_ARGS>
 struct arg_data {
   // args_[0].named_args points to named_args_ to avoid bloating format_args.
-  T args_[1 + (NUM_ARGS != 0 ? NUM_ARGS : 1)];
+  // +1 to workaround a bug in gcc 7.5 that causes duplicated-branches warning.
+  T args_[1 + (NUM_ARGS != 0 ? NUM_ARGS : +1)];
   named_arg_info<Char> named_args_[NUM_NAMED_ARGS];
 
   template <typename... U>
@@ -922,7 +923,8 @@ struct arg_data {
 
 template <typename T, typename Char, size_t NUM_ARGS>
 struct arg_data<T, Char, NUM_ARGS, 0> {
-  T args_[NUM_ARGS != 0 ? NUM_ARGS : 1];
+  // +1 to workaround a bug in gcc 7.5 that causes duplicated-branches warning.
+  T args_[NUM_ARGS != 0 ? NUM_ARGS : +1];
 
   template <typename... U>
   FMT_INLINE arg_data(const U&... init) : args_{init...} {}