diff --git a/mozglue/misc/Printf.cpp b/mozglue/misc/Printf.cpp
index de7c4a13da3a..338fc54d72bf 100644
--- a/mozglue/misc/Printf.cpp
+++ b/mozglue/misc/Printf.cpp
@@ -553,6 +553,15 @@ static bool BuildArgArray(const char* fmt, va_list ap, NumArgStateVector& nas) {
                      : sizeof(size_t) == sizeof(long) ? TYPE_LONG
                                                       : TYPE_LONGLONG;
       c = *p++;
+    } else if (c == 't') {
+      static_assert(sizeof(ptrdiff_t) == sizeof(int) ||
+                        sizeof(ptrdiff_t) == sizeof(long) ||
+                        sizeof(ptrdiff_t) == sizeof(long long),
+                    "ptrdiff_t is not one of the expected sizes");
+      nas[cn].type = sizeof(ptrdiff_t) == sizeof(int)    ? TYPE_INTN
+                     : sizeof(ptrdiff_t) == sizeof(long) ? TYPE_LONG
+                                                         : TYPE_LONGLONG;
+      c = *p++;
     }
 
     // format
@@ -831,6 +840,15 @@ bool mozilla::PrintfTarget::vprint(const char* fmt, va_list ap) {
              : sizeof(size_t) == sizeof(long) ? TYPE_LONG
                                               : TYPE_LONGLONG;
       c = *fmt++;
+    } else if (c == 't') {
+      static_assert(sizeof(ptrdiff_t) == sizeof(int) ||
+                        sizeof(ptrdiff_t) == sizeof(long) ||
+                        sizeof(ptrdiff_t) == sizeof(long long),
+                    "ptrdiff_t is not one of the expected sizes");
+      type = sizeof(ptrdiff_t) == sizeof(int)    ? TYPE_INTN
+             : sizeof(ptrdiff_t) == sizeof(long) ? TYPE_LONG
+                                                 : TYPE_LONGLONG;
+      c = *fmt++;
     }
 
     // format
diff --git a/mozglue/tests/TestPrintf.cpp b/mozglue/tests/TestPrintf.cpp
index 6a0fbec35143..d3af76f36067 100644
--- a/mozglue/tests/TestPrintf.cpp
+++ b/mozglue/tests/TestPrintf.cpp
@@ -132,7 +132,7 @@ static void TestPrintfFormats() {
   MOZ_RELEASE_ASSERT(print_one("", "%.*lld", 0, 0ll));
   MOZ_RELEASE_ASSERT(print_one("0xF0F0", "0x%llX", 0xf0f0ull));
   MOZ_RELEASE_ASSERT(print_one("27270", "%zu", (size_t)27270));
-  MOZ_RELEASE_ASSERT(print_one("27270", "%zu", (size_t)27270));
+  MOZ_RELEASE_ASSERT(print_one("27270", "%tu", (ptrdiff_t)27270));
   MOZ_RELEASE_ASSERT(print_one("hello", "he%so", "ll"));
   MOZ_RELEASE_ASSERT(print_one("hello   ", "%-8s", "hello"));
   MOZ_RELEASE_ASSERT(print_one("   hello", "%8s", "hello"));