diff --git a/widget/windows/nsClipboard.cpp b/widget/windows/nsClipboard.cpp
index 72648246790f..146ac31a17b5 100644
--- a/widget/windows/nsClipboard.cpp
+++ b/widget/windows/nsClipboard.cpp
@@ -280,18 +280,16 @@ nsresult nsClipboard::GetGlobalData(HGLOBAL aHGBL, void** aData,
                                     uint32_t* aLen) {
   // Allocate a new memory buffer and copy the data from global memory.
   // Recall that win98 allocates to nearest DWORD boundary. As a safety
-  // precaution, allocate an extra 3 bytes (but don't report them in |aLen|!)
-  // and null them out to ensure that all of our NS_strlen calls will succeed.
-  // NS_strlen operates on char16_t, so we need 3 NUL bytes to ensure it finds
-  // a full NUL char16_t when |*aLen| is odd.
+  // precaution, allocate an extra 2 bytes (but don't report them!) and
+  // null them out to ensure that all of our strlen calls will succeed.
   nsresult result = NS_ERROR_FAILURE;
   if (aHGBL != nullptr) {
     LPSTR lpStr = (LPSTR)GlobalLock(aHGBL);
     DWORD allocSize = GlobalSize(aHGBL);
-    char* data = static_cast<char*>(malloc(allocSize + 3));
+    char* data = static_cast<char*>(malloc(allocSize + sizeof(char16_t)));
     if (data) {
       memcpy(data, lpStr, allocSize);
-      data[allocSize] = data[allocSize + 1] = data[allocSize + 2]
+      data[allocSize] = data[allocSize + 1] =
           '\0';  // null terminate for safety
 
       GlobalUnlock(aHGBL);