diff --git a/tests/fmt/fuzz/CMakeLists.txt b/tests/fmt/fuzz/CMakeLists.txt
index e43606772..6f7c43da8 100644
--- a/tests/fmt/fuzz/CMakeLists.txt
+++ b/tests/fmt/fuzz/CMakeLists.txt
@@ -17,7 +17,6 @@ add_executable(
     x_test
     x_test.cc
     ../../../libs/bigint/BigUnsigned.cc
-    ../../../libs/bigint/BigInteger.cc
 )
 
 link_fuzztest(x_test)
diff --git a/tests/fmt/fuzz/x_test.cc b/tests/fmt/fuzz/x_test.cc
index 07ff7885d..ee061861f 100644
--- a/tests/fmt/fuzz/x_test.cc
+++ b/tests/fmt/fuzz/x_test.cc
@@ -4,11 +4,10 @@
 #include <sstream>
 #include "backends/cxxrtl/cxxrtl.h"
 #include "libs/bigint/BigUnsigned.hh"
-#include "libs/bigint/BigInteger.hh"
 
 using namespace cxxrtl_yosys;
 
-void Formats128BitUnsignedIntegers(chunk_t x0, chunk_t x1, chunk_t x2, chunk_t x3)
+void Formats128BitIntegers(chunk_t x0, chunk_t x1, chunk_t x2, chunk_t x3, bool signed_)
 {
   // Compare output to BigUnsigned.
   value<128> v;
@@ -16,64 +15,30 @@ void Formats128BitUnsignedIntegers(chunk_t x0, chunk_t x1, chunk_t x2, chunk_t x
   v = v.blit<63, 0>(value<64>{x3, x2});
 
   std::ostringstream oss;
-  oss << value_formatted<128>(v, false, false, ' ', 0, 10, false, false, false);
+  oss << value_formatted<128>(v, false, false, ' ', 0, 10, signed_, false, false);
   auto actual = oss.str();
 
   BigUnsigned u;
-  u.bitShiftLeft(v.slice<127, 64>().val().get<uint64_t>(), 64);
-  u.bitOr(u, v.slice<63, 0>().val().get<uint64_t>());
-
-  std::string expected;
-
-  if (u.isZero()) {
-    expected = "0";
-  } else {
-    while (!u.isZero()) {
-      expected += '0' + (u % 10).toInt();
-      u /= 10;
-    }
-    std::reverse(expected.begin(), expected.end());
-  }
-
-  EXPECT_EQ(actual, expected);
-}
-FUZZ_TEST(CxxrtlDivisionFuzz, Formats128BitUnsignedIntegers);
-
-
-void Formats128BitSignedIntegers(chunk_t x0, chunk_t x1, chunk_t x2, chunk_t x3) {
-  // Compare output to BigInteger.
-  value<128> v;
-  v = v.blit<127, 64>(value<64>{x1, x0});
-  v = v.blit<63, 0>(value<64>{x3, x2});
-
-  std::ostringstream oss;
-  oss << value_formatted<128>(v, false, false, ' ', 0, 10, true, false, false);
-  auto actual = oss.str();
-
-  BigUnsigned u;
-  bool negative = v.is_neg();
+  bool negative = signed_ && v.is_neg();
   if (negative)
     v = v.neg();
   u.bitShiftLeft(v.slice<127, 64>().val().get<uint64_t>(), 64);
   u.bitOr(u, v.slice<63, 0>().val().get<uint64_t>());
 
   std::string expected;
+
   if (u.isZero()) {
     expected = "0";
   } else {
-    // Note that we never actually do division of negative numbers: our division
-    // routines are flooring, not truncating, so dividing by 10 repeatedly won't
-    // necessarily ever get to zero.
     while (!u.isZero()) {
       expected += '0' + (u % 10).toInt();
       u /= 10;
     }
-    if (negative) {
+    if (negative)
       expected += '-';
-    }
     std::reverse(expected.begin(), expected.end());
   }
 
   EXPECT_EQ(actual, expected);
 }
-FUZZ_TEST(CxxrtlDivisionFuzz, Formats128BitSignedIntegers);
+FUZZ_TEST(CxxrtlDivisionFuzz, Formats128BitIntegers);