diff --git a/format.cc b/format.cc
index ab4b4171a706..3b502891a8d2 100644
--- a/format.cc
+++ b/format.cc
@@ -211,13 +211,13 @@ inline Arg::StringValue<wchar_t> ignore_incompatible_str(
     Arg::StringValue<wchar_t> s) { return s; }
 }  // namespace
 
-int fmt::internal::SignBitNoInline(double value) { return SignBit(value); }
+int fmt::internal::signbit_noinline(double value) { return SignBit(value); }
 
 void fmt::SystemError::init(
     int error_code, StringRef format_str, const ArgList &args) {
   error_code_ = error_code;
   Writer w;
-  internal::FormatSystemErrorMessage(w, error_code, format(format_str, args));
+  internal::format_system_error(w, error_code, format(format_str, args));
   std::runtime_error &base = *this;
   base = std::runtime_error(w.str());
 }
@@ -326,7 +326,7 @@ void fmt::WindowsError::init(
     int error_code, StringRef format_str, const ArgList &args) {
   error_code_ = error_code;
   Writer w;
-  internal::FormatWinErrorMessage(w, error_code, format(format_str, args));
+  internal::format_windows_error(w, error_code, format(format_str, args));
   std::runtime_error &base = *this;
   base = std::runtime_error(w.str());
 }
@@ -361,7 +361,7 @@ int fmt::internal::safe_strerror(
   return result;
 }
 
-void fmt::internal::FormatSystemErrorMessage(
+void fmt::internal::format_system_error(
     fmt::Writer &out, int error_code, fmt::StringRef message) {
   Array<char, INLINE_BUFFER_SIZE> buffer;
   buffer.resize(INLINE_BUFFER_SIZE);
@@ -382,7 +382,7 @@ void fmt::internal::FormatSystemErrorMessage(
 }
 
 #ifdef _WIN32
-void fmt::internal::FormatWinErrorMessage(
+void fmt::internal::format_windows_error(
     fmt::Writer &out, int error_code, fmt::StringRef message) {
   class String {
    private:
@@ -1123,15 +1123,15 @@ void fmt::BasicFormatter<Char>::Format(
 
 void fmt::ReportSystemError(
     int error_code, fmt::StringRef message) FMT_NOEXCEPT(true) {
-  // FIXME: FormatSystemErrorMessage may throw
-  ReportError(internal::FormatSystemErrorMessage, error_code, message);
+  // FIXME: format_system_error may throw
+  ReportError(internal::format_system_error, error_code, message);
 }
 
 #ifdef _WIN32
 void fmt::ReportWinError(
     int error_code, fmt::StringRef message) FMT_NOEXCEPT(true) {
-  // FIXME: FormatWinErrorMessage may throw
-  ReportError(internal::FormatWinErrorMessage, error_code, message);
+  // FIXME: format_windows_error may throw
+  ReportError(internal::format_windows_error, error_code, message);
 }
 #endif
 
diff --git a/format.h b/format.h
index 55c598ed5c0a..c25825c48c60 100644
--- a/format.h
+++ b/format.h
@@ -410,7 +410,7 @@ inline bool is_negative(T value) {
   return SignChecker<std::numeric_limits<T>::is_signed>::is_negative(value);
 }
 
-int SignBitNoInline(double value);
+int signbit_noinline(double value);
 
 template <typename T>
 struct IntTraits {
@@ -537,11 +537,11 @@ class UTF16ToUTF8 {
 int safe_strerror(int error_code,
     char *&buffer, std::size_t buffer_size) FMT_NOEXCEPT(true);
 
-void FormatSystemErrorMessage(
+void format_system_error(
     fmt::Writer &out, int error_code, fmt::StringRef message);
 
 #ifdef _WIN32
-void FormatWinErrorMessage(
+void format_windows_error(
     fmt::Writer &out, int error_code, fmt::StringRef message);
 #endif
 
diff --git a/test/format-test.cc b/test/format-test.cc
index 96ad67021759..b2b3ae107fc0 100644
--- a/test/format-test.cc
+++ b/test/format-test.cc
@@ -1229,7 +1229,7 @@ TEST(FormatterTest, FormatNaN) {
   double nan = std::numeric_limits<double>::quiet_NaN();
   EXPECT_EQ("nan", format("{}", nan));
   EXPECT_EQ("+nan", format("{:+}", nan));
-  if (fmt::internal::SignBitNoInline(-nan))
+  if (fmt::internal::signbit_noinline(-nan))
     EXPECT_EQ("-nan", format("{}", -nan));
   else
     fmt::print("Warning: compiler doesn't handle negative NaN correctly");
diff --git a/test/gtest-extra-test.cc b/test/gtest-extra-test.cc
index 1083217b3f59..513157b798f0 100644
--- a/test/gtest-extra-test.cc
+++ b/test/gtest-extra-test.cc
@@ -308,8 +308,8 @@ TEST(ExpectTest, EXPECT_SYSTEM_ERROR) {
           "ThrowSystemError() throws an exception with a different message.\n"
           "Expected: {}\n"
           "  Actual: {}",
-          FormatSystemErrorMessage(EDOM, "other"),
-          FormatSystemErrorMessage(EDOM, "test")));
+          format_system_error(EDOM, "other"),
+          format_system_error(EDOM, "test")));
 }
 
 // Tests EXPECT_WRITE.
@@ -347,10 +347,10 @@ TEST(StreamingAssertionsTest, EXPECT_WRITE) {
       << "expected failure", "expected failure");
 }
 
-TEST(UtilTest, FormatSystemErrorMessage) {
+TEST(UtilTest, FormatSystemError) {
   fmt::Writer out;
-  fmt::internal::FormatSystemErrorMessage(out, EDOM, "test message");
-  EXPECT_EQ(out.str(), FormatSystemErrorMessage(EDOM, "test message"));
+  fmt::internal::format_system_error(out, EDOM, "test message");
+  EXPECT_EQ(out.str(), format_system_error(EDOM, "test message"));
 }
 
 #if FMT_USE_FILE_DESCRIPTORS
@@ -500,7 +500,7 @@ TEST(BufferedFileTest, CloseErrorInDtor) {
       // redirection.
       FMT_POSIX(close(f->fileno()));
       SUPPRESS_ASSERT(delete f);
-  }, FormatSystemErrorMessage(EBADF, "cannot close file") + "\n");
+  }, format_system_error(EBADF, "cannot close file") + "\n");
 }
 
 TEST(BufferedFileTest, Close) {
@@ -624,7 +624,7 @@ TEST(FileTest, CloseErrorInDtor) {
       // redirection.
       FMT_POSIX(close(f->descriptor()));
       SUPPRESS_ASSERT(delete f);
-  }, FormatSystemErrorMessage(EBADF, "cannot close file") + "\n");
+  }, format_system_error(EBADF, "cannot close file") + "\n");
 }
 
 TEST(FileTest, Close) {
@@ -825,7 +825,7 @@ TEST(OutputRedirectTest, ErrorInDtor) {
       // redirection.
       FMT_POSIX(close(write_fd));
       SUPPRESS_ASSERT(delete redir);
-  }, FormatSystemErrorMessage(EBADF, "cannot flush stream"));
+  }, format_system_error(EBADF, "cannot flush stream"));
   write_copy.dup2(write_fd); // "undo" close or dtor of BufferedFile will fail
 }
 
diff --git a/test/gtest-extra.cc b/test/gtest-extra.cc
index 3717645d4e17..e09368da1c4e 100644
--- a/test/gtest-extra.cc
+++ b/test/gtest-extra.cc
@@ -91,8 +91,8 @@ std::string OutputRedirect::RestoreAndRead() {
 
 #endif  // FMT_USE_FILE_DESCRIPTORS
 
-std::string FormatSystemErrorMessage(int error_code, fmt::StringRef message) {
+std::string format_system_error(int error_code, fmt::StringRef message) {
   fmt::Writer out;
-  fmt::internal::FormatSystemErrorMessage(out, error_code, message);
+  fmt::internal::format_system_error(out, error_code, message);
   return out.str();
 }
diff --git a/test/gtest-extra.h b/test/gtest-extra.h
index b476fa0c604a..5058fdd8b44a 100644
--- a/test/gtest-extra.h
+++ b/test/gtest-extra.h
@@ -81,11 +81,11 @@
   FMT_TEST_THROW_(statement, expected_exception, \
       expected_message, GTEST_NONFATAL_FAILURE_)
 
-std::string FormatSystemErrorMessage(int error_code, fmt::StringRef message);
+std::string format_system_error(int error_code, fmt::StringRef message);
 
 #define EXPECT_SYSTEM_ERROR(statement, error_code, message) \
   EXPECT_THROW_MSG(statement, fmt::SystemError, \
-      FormatSystemErrorMessage(error_code, message))
+      format_system_error(error_code, message))
 
 #if FMT_USE_FILE_DESCRIPTORS
 
diff --git a/test/posix-test.cc b/test/posix-test.cc
index 3a63019cde2c..95391dcefaf9 100644
--- a/test/posix-test.cc
+++ b/test/posix-test.cc
@@ -169,7 +169,7 @@ TEST(FileTest, CloseNoRetryInDtor) {
     delete f;
     saved_close_count = close_count;
     close_count = 0;
-  }, FormatSystemErrorMessage(EINTR, "cannot close file") + "\n");
+  }, format_system_error(EINTR, "cannot close file") + "\n");
   EXPECT_EQ(2, saved_close_count);
 }
 
@@ -299,7 +299,7 @@ TEST(BufferedFileTest, CloseNoRetryInDtor) {
     delete f;
     saved_fclose_count = fclose_count;
     fclose_count = 0;
-  }, FormatSystemErrorMessage(EINTR, "cannot close file") + "\n");
+  }, format_system_error(EINTR, "cannot close file") + "\n");
   EXPECT_EQ(2, saved_fclose_count);
 }
 
diff --git a/test/util-test.cc b/test/util-test.cc
index 4b51cd7f65be..58874a5a003a 100644
--- a/test/util-test.cc
+++ b/test/util-test.cc
@@ -387,7 +387,7 @@ TEST(UtilTest, UTF8ToUTF16) {
 template <typename Converter>
 void CheckUTFConversionError(const char *message) {
   fmt::Writer out;
-  fmt::internal::FormatWinErrorMessage(out, ERROR_INVALID_PARAMETER, message);
+  fmt::internal::format_windows_error(out, ERROR_INVALID_PARAMETER, message);
   fmt::SystemError error(0, "");
   try {
     Converter(0);
@@ -471,20 +471,20 @@ void CheckThrowError(int error_code, FormatErrorMessage format) {
   EXPECT_EQ(error_code, error.error_code());
 }
 
-TEST(UtilTest, FormatSystemErrorMessage) {
+TEST(UtilTest, FormatSystemError) {
   fmt::Writer message;
-  fmt::internal::FormatSystemErrorMessage(message, EDOM, "test");
+  fmt::internal::format_system_error(message, EDOM, "test");
   EXPECT_EQ(fmt::format("test: {}",
           GetSystemErrorMessage(EDOM)), message.str());
 }
 
 TEST(UtilTest, ThrowSystemError) {
-  CheckThrowError<fmt::SystemError>(EDOM, fmt::internal::FormatSystemErrorMessage);
+  CheckThrowError<fmt::SystemError>(EDOM, fmt::internal::format_system_error);
 }
 
 TEST(UtilTest, ReportSystemError) {
   fmt::Writer out;
-  fmt::internal::FormatSystemErrorMessage(out, EDOM, "test error");
+  fmt::internal::format_system_error(out, EDOM, "test error");
   out << '\n';
   EXPECT_WRITE(stderr, fmt::ReportSystemError(EDOM, "test error"), out.str());
 }
@@ -500,7 +500,7 @@ TEST(UtilTest, FormatWinErrorMessage) {
   fmt::internal::UTF16ToUTF8 utf8_message(message);
   LocalFree(message);
   fmt::Writer actual_message;
-  fmt::internal::FormatWinErrorMessage(
+  fmt::internal::format_windows_error(
       actual_message, ERROR_FILE_EXISTS, "test");
   EXPECT_EQ(fmt::format("test: {}", utf8_message.str()),
       actual_message.str());
@@ -508,12 +508,12 @@ TEST(UtilTest, FormatWinErrorMessage) {
 
 TEST(UtilTest, ThrowWinError) {
   CheckThrowError<fmt::WindowsError>(
-      ERROR_FILE_EXISTS, fmt::internal::FormatWinErrorMessage);
+      ERROR_FILE_EXISTS, fmt::internal::format_windows_error);
 }
 
 TEST(UtilTest, ReportWinError) {
   fmt::Writer out;
-  fmt::internal::FormatWinErrorMessage(out, ERROR_FILE_EXISTS, "test error");
+  fmt::internal::format_windows_error(out, ERROR_FILE_EXISTS, "test error");
   out << '\n';
   EXPECT_WRITE(stderr,
       fmt::ReportWinError(ERROR_FILE_EXISTS, "test error"), out.str());