diff --git a/format.cc b/format.cc
index 2790e3b6..3f5d8080 100644
--- a/format.cc
+++ b/format.cc
@@ -118,6 +118,8 @@ void ReportError(FormatFunc func,
 }
 }  // namespace
 
+int fmt::internal::SignBitNoInline(double value) { return SignBit(value); }
+
 template <typename T>
 int fmt::internal::CharTraits<char>::FormatFloat(
     char *buffer, std::size_t size, const char *format,
diff --git a/format.h b/format.h
index 0fbddde6..dcfde293 100644
--- a/format.h
+++ b/format.h
@@ -399,6 +399,8 @@ inline bool IsNegative(T value) {
   return SignChecker<std::numeric_limits<T>::is_signed>::IsNegative(value);
 }
 
+int SignBitNoInline(double value);
+
 template <typename T>
 struct IntTraits {
   // Smallest of uint32_t and uint64_t that is large enough to represent
diff --git a/test/format-test.cc b/test/format-test.cc
index ece86785..07872dd8 100644
--- a/test/format-test.cc
+++ b/test/format-test.cc
@@ -1235,8 +1235,7 @@ TEST(FormatterTest, FormatNaN) {
   double nan = std::numeric_limits<double>::quiet_NaN();
   EXPECT_EQ("nan", str(Format("{}") << nan));
   EXPECT_EQ("+nan", str(Format("{:+}") << nan));
-  using namespace std;
-  if (signbit(-nan))
+  if (fmt::internal::SignBitNoInline(-nan))
     EXPECT_EQ("-nan", str(Format("{}") << -nan));
   else
     fmt::Print("Warning: compiler doesn't handle negative NaN correctly");