diff --git a/format.h b/format.h
index 3a82f8272c0f..8d54bf521c78 100644
--- a/format.h
+++ b/format.h
@@ -800,6 +800,10 @@ struct EnableIf {};
 template<class T>
 struct EnableIf<true, T> { typedef T type; };
 
+// A helper function to suppress bogus "conditional expression is constant"
+// warnings.
+inline bool check(bool value) { return value; }
+
 // Makes an Arg object from any type.
 template <typename Char>
 class MakeValue : public Arg {
@@ -859,7 +863,7 @@ class MakeValue : public Arg {
   MakeValue(long value) {
     // To minimize the number of types we need to deal with, long is
     // translated either to int or to long long depending on its size.
-    if (sizeof(long) == sizeof(int))
+    if (check(sizeof(long) == sizeof(int)))
       int_value = static_cast<int>(value);
     else
       long_long_value = value;
@@ -869,7 +873,7 @@ class MakeValue : public Arg {
   }
 
   MakeValue(unsigned long value) {
-    if (sizeof(unsigned long) == sizeof(unsigned))
+    if (check(sizeof(unsigned long) == sizeof(unsigned)))
       uint_value = static_cast<unsigned>(value);
     else
       ulong_long_value = value;
@@ -2634,7 +2638,7 @@ struct ArgArraySize {
     Arg array[fmt::internal::ArgArraySize<sizeof...(Args)>::VALUE] = { \
       fmt::internal::MakeValue<Char>(args)... \
     }; \
-    if (sizeof...(Args) > fmt::ArgList::MAX_PACKED_ARGS) \
+    if (fmt::internal::check((sizeof...(Args) > fmt::ArgList::MAX_PACKED_ARGS))) \
       set_types(array, args...); \
     call(FMT_FOR_EACH(FMT_GET_ARG_NAME, __VA_ARGS__), \
       fmt::ArgList(fmt::internal::make_type(args...), array)); \