diff --git a/llvm/lib/BinaryFormat/Magic.cpp b/llvm/lib/BinaryFormat/Magic.cpp
index db8e952..42546ea 100644
--- a/llvm/lib/BinaryFormat/Magic.cpp
+++ b/llvm/lib/BinaryFormat/Magic.cpp
@@ -185,8 +185,8 @@
     if (startswith(Magic, "MZ") && Magic.size() >= 0x3c + 4) {
       uint32_t off = read32le(Magic.data() + 0x3c);
       // PE/COFF file, either EXE or DLL.
-      if (off + sizeof(COFF::PEMagic) <= Magic.size() &&
-          memcmp(Magic.data() + off, COFF::PEMagic, sizeof(COFF::PEMagic)) == 0)
+      if (Magic.substr(off).startswith(
+              StringRef(COFF::PEMagic, sizeof(COFF::PEMagic))))
         return file_magic::pecoff_executable;
     }
     break;