diff --git a/format.cc b/format.cc
index d31db457..78b54d65 100644
--- a/format.cc
+++ b/format.cc
@@ -157,11 +157,14 @@ void fmt::Formatter::FormatDouble(
     T value, unsigned flags, int width, int precision, char type) {
   // Check type.
   switch (type) {
+  case 0:
+    type = 'g';
+    break;
   case 'e': case 'E': case 'f': case 'F': case 'g': case 'G':
     break;
   default:
-    // TODO: error
-    break;
+    throw FormatError(
+        str(fmt::Format("unknown format code '{0}' for double") << type));
   }
 
   // Build format string.
@@ -181,7 +184,7 @@ void fmt::Formatter::FormatDouble(
   }
   if (IsLongDouble<T>::VALUE)
     *format_ptr++ = 'L';
-  *format_ptr++ = type ? type : 'g';
+  *format_ptr++ = type;
   *format_ptr = '\0';
 
   // Format using snprintf.
diff --git a/format_test.cc b/format_test.cc
index 83797877..6004ffc6 100644
--- a/format_test.cc
+++ b/format_test.cc
@@ -258,11 +258,19 @@ TEST(FormatterTest, Precision) {
       FormatError, "precision specifier requires floating-point argument");
 }
 
-TEST(FormatterTest, Type) {
+TEST(FormatterTest, FormatInt) {
   EXPECT_THROW_MSG(Format("{0:v") << 42,
       FormatError, "unmatched '{' in format");
   EXPECT_THROW_MSG(Format("{0:v}") << 42,
       FormatError, "unknown format code 'v' for integer");
+  EXPECT_THROW_MSG(Format("{0:c}") << 42,
+      FormatError, "unknown format code 'c' for integer");
+  EXPECT_THROW_MSG(Format("{0:e}") << 42,
+      FormatError, "unknown format code 'e' for integer");
+  EXPECT_THROW_MSG(Format("{0:f}") << 42,
+      FormatError, "unknown format code 'f' for integer");
+  EXPECT_THROW_MSG(Format("{0:g}") << 42,
+      FormatError, "unknown format code 'g' for integer");
 }
 
 TEST(FormatterTest, FormatDec) {
@@ -333,6 +341,40 @@ TEST(FormatterTest, FormatOct) {
   EXPECT_EQ(buffer, str(Format("{0:o}") << ULONG_MAX));
 }
 
+TEST(FormatterTest, FormatDouble) {
+  EXPECT_THROW_MSG(Format("{0:c}") << 1.2,
+      FormatError, "unknown format code 'c' for double");
+  EXPECT_THROW_MSG(Format("{0:d}") << 1.2,
+      FormatError, "unknown format code 'd' for double");
+  EXPECT_THROW_MSG(Format("{0:o}") << 1.2,
+      FormatError, "unknown format code 'o' for double");
+  EXPECT_THROW_MSG(Format("{0:x}") << 1.2,
+      FormatError, "unknown format code 'x' for double");
+  EXPECT_EQ("0", str(Format("{0:}") << 0.0));
+  EXPECT_EQ("0.000000", str(Format("{0:f}") << 0.0));
+  EXPECT_EQ("392.65", str(Format("{0:}") << 392.65));
+  EXPECT_EQ("392.65", str(Format("{0:g}") << 392.65));
+  EXPECT_EQ("392.65", str(Format("{0:G}") << 392.65));
+  EXPECT_EQ("392.650000", str(Format("{0:f}") << 392.65));
+  EXPECT_EQ("392.650000", str(Format("{0:F}") << 392.65));
+  EXPECT_EQ("3.926500e+02", str(Format("{0:e}") << 392.65));
+  EXPECT_EQ("3.926500E+02", str(Format("{0:E}") << 392.65));
+  EXPECT_EQ("+0000392.6", str(Format("{0:+010.4g}") << 392.65));
+}
+
+TEST(FormatterTest, FormatLongDouble) {
+  EXPECT_EQ("0", str(Format("{0:}") << 0.0l));
+  EXPECT_EQ("0.000000", str(Format("{0:f}") << 0.0l));
+  EXPECT_EQ("392.65", str(Format("{0:}") << 392.65l));
+  EXPECT_EQ("392.65", str(Format("{0:g}") << 392.65l));
+  EXPECT_EQ("392.65", str(Format("{0:G}") << 392.65l));
+  EXPECT_EQ("392.650000", str(Format("{0:f}") << 392.65l));
+  EXPECT_EQ("392.650000", str(Format("{0:F}") << 392.65l));
+  EXPECT_EQ("3.926500e+02", str(Format("{0:e}") << 392.65l));
+  EXPECT_EQ("3.926500E+02", str(Format("{0:E}") << 392.65l));
+  EXPECT_EQ("+0000392.6", str(Format("{0:+010.4g}") << 392.65l));
+}
+
 TEST(FormatterTest, FormatChar) {
   EXPECT_EQ("a*b", str(Format("{0}{1}{2}") << 'a' << '*' << 'b'));
 }