diff --git a/format.h b/format.h
index d3d00bcc..e75bced1 100644
--- a/format.h
+++ b/format.h
@@ -1140,7 +1140,7 @@ class FormatInt {
 
  public:
   explicit FormatInt(int value) {
-    uint64_t abs_value = value;
+    unsigned abs_value = value;
     bool negative = value < 0;
     if (negative)
       abs_value = 0 - value;
diff --git a/format_test.cc b/format_test.cc
index c9e8357c..b57390f3 100644
--- a/format_test.cc
+++ b/format_test.cc
@@ -1287,6 +1287,7 @@ TEST(FormatterTest, Examples) {
 
 TEST(FormatIntTest, FormatInt) {
   EXPECT_EQ("42", fmt::FormatInt(42).str());
+  EXPECT_EQ("-42", fmt::FormatInt(-42).str());
 }
 
 template <typename T>