diff --git a/llvm/lib/ExecutionEngine/JITLink/JITLinkMemoryManager.cpp b/llvm/lib/ExecutionEngine/JITLink/JITLinkMemoryManager.cpp
index 0e5ed8e3d1ce3..4fb349255f75c 100644
--- a/llvm/lib/ExecutionEngine/JITLink/JITLinkMemoryManager.cpp
+++ b/llvm/lib/ExecutionEngine/JITLink/JITLinkMemoryManager.cpp
@@ -40,8 +40,9 @@ Error toError(CWrapperFunctionResult R) {
     char *Content = Large ? R.Data.ValuePtr : R.Data.Value;
     if (Content[0]) {
       HasError = true;
-      ErrMsg.resize(R.Size - 1);
-      memcpy(&ErrMsg[0], Content + 1, R.Size - 1);
+      constexpr unsigned StrStart = 1 + sizeof(uint64_t);
+      ErrMsg.resize(R.Size - StrStart);
+      memcpy(&ErrMsg[0], Content + StrStart, R.Size - StrStart);
     }
     if (Large)
       free(R.Data.ValuePtr);