diff --git a/lang/c++/impl/FileStream.cc b/lang/c++/impl/FileStream.cc
index 9063cf1f734..debe87c0110 100644
--- a/lang/c++/impl/FileStream.cc
+++ b/lang/c++/impl/FileStream.cc
@@ -205,8 +205,15 @@ class BufferCopyInInputStream : public SeekableInputStream {
     void seek(int64_t position) final {
         // BufferCopyIn::seek is relative to byteCount_, whereas position is
         // absolute.
-        in_->seek(position - byteCount_ - available_);
-        byteCount_ = position;
+        int64_t offset = position - static_cast<int64_t>(byteCount_) - static_cast<int64_t>(available_);
+        if (offset < 0) {
+            throw Exception("Negative offset in seek");
+        }
+        in_->seek(static_cast<size_t>(offset));
+        if (position < 0) {
+            throw Exception("Negative position not allowed");
+        }
+        byteCount_ = static_cast<size_t>(position);
         available_ = 0;
     }
 
diff --git a/lang/c++/impl/parsing/Symbol.cc b/lang/c++/impl/parsing/Symbol.cc
index fe87c5205b4..9322fc60bf9 100644
--- a/lang/c++/impl/parsing/Symbol.cc
+++ b/lang/c++/impl/parsing/Symbol.cc
@@ -88,7 +88,12 @@ Symbol Symbol::enumAdjustSymbol(const NodePtr &writer, const NodePtr &reader) {
             adj.push_back(static_cast<int>(-pos));
             err.push_back(s);
         } else {
-            adj.push_back(static_cast<int>(it - rs.begin()));
+            auto index = it - rs.begin();
+            if constexpr (std::is_same_v<decltype(index), int>) {
+                adj.push_back(index);  // 32-bit: already int
+            } else {
+                adj.push_back(static_cast<int>(index));  // 64-bit: long to int
+            }
         }
     }
     return Symbol(Kind::EnumAdjust, make_pair(adj, err));