diff --git a/include/fmt/format-inl.h b/include/fmt/format-inl.h
index 5e6bfdc8..d301e972 100644
--- a/include/fmt/format-inl.h
+++ b/include/fmt/format-inl.h
@@ -1153,13 +1153,13 @@ int snprintf_float(T value, int precision, float_spec spec, buffer<char>& buf) {
                      ? snprintf_ptr(begin, capacity, format, precision, value)
                      : snprintf_ptr(begin, capacity, format, value);
     if (result < 0) {
-      buf.reserve(capacity + 1);  // The buffer will grow exponentially.
+      buf.reserve(buf.capacity() + 1);  // The buffer will grow exponentially.
       continue;
     }
     unsigned size = to_unsigned(result);
     // Size equal to capacity means that the last character was truncated.
     if (size >= capacity) {
-      buf.reserve(size + 1);  // Add 1 for the terminating '\0'.
+      buf.reserve(size + offset + 1);  // Add 1 for the terminating '\0'.
       continue;
     }
     auto is_digit = [](char c) { return c >= '0' && c <= '9'; };
diff --git a/test/format-test.cc b/test/format-test.cc
index bce5539f..e747a407 100644
--- a/test/format-test.cc
+++ b/test/format-test.cc
@@ -1212,6 +1212,20 @@ TEST(FormatterTest, Precision) {
       "012970999954193198940908041656332452475714786901472678015935523861155013"
       "480352649347201937902681071074917033322268447533357208324319361e-324",
       format("{:.494}", 4.9406564584124654E-324));
+  EXPECT_EQ(
+      "-0X1.41FE3FFE71C9E000000000000000000000000000000000000000000000000000000"
+      "000000000000000000000000000000000000000000000000000000000000000000000000"
+      "000000000000000000000000000000000000000000000000000000000000000000000000"
+      "000000000000000000000000000000000000000000000000000000000000000000000000"
+      "000000000000000000000000000000000000000000000000000000000000000000000000"
+      "000000000000000000000000000000000000000000000000000000000000000000000000"
+      "000000000000000000000000000000000000000000000000000000000000000000000000"
+      "000000000000000000000000000000000000000000000000000000000000000000000000"
+      "000000000000000000000000000000000000000000000000000000000000000000000000"
+      "000000000000000000000000000000000000000000000000000000000000000000000000"
+      "000000000000000000000000000000000000000000000000000000000000000000000000"
+      "000000000000000000000000000000000000000000000000000P+127",
+      format("{:.838A}", -2.14001164E+38));
   EXPECT_EQ("123.", format("{:#.0f}", 123.0));
 
   EXPECT_THROW_MSG(format("{0:.2}", reinterpret_cast<void*>(0xcafe)),