diff --git a/src/crypto/fipsmodule/bn/bn_test.cc b/src/crypto/fipsmodule/bn/bn_test.cc
index 01dcfbb16..e4720b1b3 100644
--- a/src/crypto/fipsmodule/bn/bn_test.cc
+++ b/src/crypto/fipsmodule/bn/bn_test.cc
@@ -74,6 +74,7 @@
 #include <string.h>
 
 #include <algorithm>
+#include <limits>
 #include <utility>
 
 #include <gtest/gtest.h>
@@ -2796,6 +2797,27 @@ TEST_F(BNTest, MontgomeryLarge) {
                                          ctx(), nullptr));
 }
 
+TEST_F(BNTest, FormatWord) {
+  char buf[32];
+  snprintf(buf, sizeof(buf), BN_DEC_FMT1, BN_ULONG{1234});
+  EXPECT_STREQ(buf, "1234");
+  snprintf(buf, sizeof(buf), BN_HEX_FMT1, BN_ULONG{1234});
+  EXPECT_STREQ(buf, "4d2");
+
+  // |BN_HEX_FMT2| is zero-padded up to the maximum value.
+#if defined(OPENSSL_64_BIT)
+  snprintf(buf, sizeof(buf), BN_HEX_FMT2, BN_ULONG{1234});
+  EXPECT_STREQ(buf, "00000000000004d2");
+  snprintf(buf, sizeof(buf), BN_HEX_FMT2, std::numeric_limits<BN_ULONG>::max());
+  EXPECT_STREQ(buf, "ffffffffffffffff");
+#else
+  snprintf(buf, sizeof(buf), BN_HEX_FMT2, BN_ULONG{1234});
+  EXPECT_STREQ(buf, "000004d2");
+  snprintf(buf, sizeof(buf), BN_HEX_FMT2, std::numeric_limits<BN_ULONG>::max());
+  EXPECT_STREQ(buf, "ffffffff");
+#endif
+}
+
 #if defined(SUPPORTS_ABI_TEST)
 // These functions are not always implemented in assembly, but they sometimes
 // are, so include ABI tests for each.
diff --git a/src/include/openssl/bn.h b/src/include/openssl/bn.h
index a03e41f18..0361645ab 100644
--- a/src/include/openssl/bn.h
+++ b/src/include/openssl/bn.h
@@ -160,14 +160,12 @@ extern "C" {
 typedef uint64_t BN_ULONG;
 #define BN_BITS2 64
 #define BN_DEC_FMT1 "%" PRIu64
-#define BN_DEC_FMT2 "%019" PRIu64
 #define BN_HEX_FMT1 "%" PRIx64
 #define BN_HEX_FMT2 "%016" PRIx64
 #elif defined(OPENSSL_32_BIT)
 typedef uint32_t BN_ULONG;
 #define BN_BITS2 32
 #define BN_DEC_FMT1 "%" PRIu32
-#define BN_DEC_FMT2 "%09" PRIu32
 #define BN_HEX_FMT1 "%" PRIx32
 #define BN_HEX_FMT2 "%08" PRIx32
 #else