diff --git a/src/client/linux/minidump_writer/linux_ptrace_dumper.cc b/src/client/linux/minidump_writer/linux_ptrace_dumper.cc
index 5591067a..3863d79f 100644
--- a/src/client/linux/minidump_writer/linux_ptrace_dumper.cc
+++ b/src/client/linux/minidump_writer/linux_ptrace_dumper.cc
@@ -112,13 +112,13 @@ bool LinuxPtraceDumper::BuildProcPath(char* path, pid_t pid,
   if (node_len == 0)
     return false;
 
-  const unsigned pid_len = my_int_len(pid);
+  const unsigned pid_len = my_uint_len(pid);
   const size_t total_length = 6 + pid_len + 1 + node_len;
   if (total_length >= NAME_MAX)
     return false;
 
   my_memcpy(path, "/proc/", 6);
-  my_itos(path + 6, pid, pid_len);
+  my_uitos(path + 6, pid, pid_len);
   path[6 + pid_len] = '/';
   my_memcpy(path + 6 + pid_len + 1, node, node_len);
   path[total_length] = '\0';
diff --git a/src/common/linux/linux_libc_support.cc b/src/common/linux/linux_libc_support.cc
index 39e2aa1e..845729c9 100644
--- a/src/common/linux/linux_libc_support.cc
+++ b/src/common/linux/linux_libc_support.cc
@@ -95,9 +95,8 @@ bool my_strtoui(int* result, const char* s) {
   return true;
 }
 
-// Return the length of the given, non-negative integer when expressed in base
-// 10.
-unsigned my_int_len(intmax_t i) {
+// Return the length of the given unsigned integer when expressed in base 10.
+unsigned my_uint_len(uintmax_t i) {
   if (!i)
     return 1;
 
@@ -110,13 +109,13 @@ unsigned my_int_len(intmax_t i) {
   return len;
 }
 
-// Convert a non-negative integer to a string
+// Convert an unsigned integer to a string
 //   output: (output) the resulting string is written here. This buffer must be
-//     large enough to hold the resulting string. Call |my_int_len| to get the
+//     large enough to hold the resulting string. Call |my_uint_len| to get the
 //     required length.
-//   i: the non-negative integer to serialise.
-//   i_len: the length of the integer in base 10 (see |my_int_len|).
-void my_itos(char* output, intmax_t i, unsigned i_len) {
+//   i: the unsigned integer to serialise.
+//   i_len: the length of the integer in base 10 (see |my_uint_len|).
+void my_uitos(char* output, uintmax_t i, unsigned i_len) {
   for (unsigned index = i_len; index; --index, i /= 10)
     output[index - 1] = '0' + (i % 10);
 }
diff --git a/src/common/linux/linux_libc_support.h b/src/common/linux/linux_libc_support.h
index b2f47af8..011048f8 100644
--- a/src/common/linux/linux_libc_support.h
+++ b/src/common/linux/linux_libc_support.h
@@ -52,17 +52,16 @@ extern int my_strncmp(const char* a, const char* b, size_t len);
 // Return true iff successful.
 extern bool my_strtoui(int* result, const char* s);
 
-// Return the length of the given, non-negative integer when expressed in base
-// 10.
-extern unsigned my_int_len(intmax_t i);
+// Return the length of the given unsigned integer when expressed in base 10.
+extern unsigned my_uint_len(uintmax_t i);
 
-// Convert a non-negative integer to a string
+// Convert an unsigned integer to a string
 //   output: (output) the resulting string is written here. This buffer must be
 //     large enough to hold the resulting string. Call |my_int_len| to get the
 //     required length.
-//   i: the non-negative integer to serialise.
-//   i_len: the length of the integer in base 10 (see |my_int_len|).
-extern void my_itos(char* output, intmax_t i, unsigned i_len);
+//   i: the unsigned integer to serialise.
+//   i_len: the length of the integer in base 10 (see |my_uint_len|).
+extern void my_uitos(char* output, uintmax_t i, unsigned i_len);
 
 extern const char* my_strchr(const char* haystack, char needle);
 
diff --git a/src/common/linux/linux_libc_support_unittest.cc b/src/common/linux/linux_libc_support_unittest.cc
index 7f974af8..2a9694ce 100644
--- a/src/common/linux/linux_libc_support_unittest.cc
+++ b/src/common/linux/linux_libc_support_unittest.cc
@@ -89,35 +89,41 @@ TEST(LinuxLibcSupportTest, strtoui) {
   ASSERT_EQ(result, 123);
 }
 
-TEST(LinuxLibcSupportTest, int_len) {
-  ASSERT_EQ(my_int_len(0), 1);
-  ASSERT_EQ(my_int_len(2), 1);
-  ASSERT_EQ(my_int_len(5), 1);
-  ASSERT_EQ(my_int_len(9), 1);
-  ASSERT_EQ(my_int_len(10), 2);
-  ASSERT_EQ(my_int_len(99), 2);
-  ASSERT_EQ(my_int_len(100), 3);
-  ASSERT_EQ(my_int_len(101), 3);
-  ASSERT_EQ(my_int_len(1000), 4);
+TEST(LinuxLibcSupportTest, uint_len) {
+  ASSERT_EQ(my_uint_len(0), 1);
+  ASSERT_EQ(my_uint_len(2), 1);
+  ASSERT_EQ(my_uint_len(5), 1);
+  ASSERT_EQ(my_uint_len(9), 1);
+  ASSERT_EQ(my_uint_len(10), 2);
+  ASSERT_EQ(my_uint_len(99), 2);
+  ASSERT_EQ(my_uint_len(100), 3);
+  ASSERT_EQ(my_uint_len(101), 3);
+  ASSERT_EQ(my_uint_len(1000), 4);
+  // 0xFFFFFFFFFFFFFFFF
+  ASSERT_EQ(my_uint_len(18446744073709551615LLU), 20);
 }
 
-TEST(LinuxLibcSupportTest, itos) {
-  char buf[10];
+TEST(LinuxLibcSupportTest, uitos) {
+  char buf[32];
 
-  my_itos(buf, 0, 1);
+  my_uitos(buf, 0, 1);
   ASSERT_EQ(0, memcmp(buf, "0", 1));
 
-  my_itos(buf, 1, 1);
+  my_uitos(buf, 1, 1);
   ASSERT_EQ(0, memcmp(buf, "1", 1));
 
-  my_itos(buf, 10, 2);
+  my_uitos(buf, 10, 2);
   ASSERT_EQ(0, memcmp(buf, "10", 2));
 
-  my_itos(buf, 63, 2);
+  my_uitos(buf, 63, 2);
   ASSERT_EQ(0, memcmp(buf, "63", 2));
 
-  my_itos(buf, 101, 3);
+  my_uitos(buf, 101, 3);
   ASSERT_EQ(0, memcmp(buf, "101", 2));
+
+  // 0xFFFFFFFFFFFFFFFF
+  my_uitos(buf, 18446744073709551615LLU, 20);
+  ASSERT_EQ(0, memcmp(buf, "18446744073709551615", 20));
 }
 
 TEST(LinuxLibcSupportTest, strchr) {