diff --git a/flang/include/flang/Common/interval.h b/flang/include/flang/Common/interval.h
--- a/flang/include/flang/Common/interval.h
+++ b/flang/include/flang/Common/interval.h
@@ -93,7 +93,7 @@
     return x - start_;
   }
   A OffsetMember(std::size_t n) const {
-    CHECK(n < size_);
+    CHECK(n <= size_);
     return start_ + n;
   }
 
diff --git a/flang/lib/Parser/provenance.cpp b/flang/lib/Parser/provenance.cpp
--- a/flang/lib/Parser/provenance.cpp
+++ b/flang/lib/Parser/provenance.cpp
@@ -91,7 +91,10 @@
 }
 
 ProvenanceRange OffsetToProvenanceMappings::Map(std::size_t at) const {
-  //  CHECK(!provenanceMap_.empty());
+  if (provenanceMap_.empty()) {
+    CHECK(at == 0);
+    return {};
+  }
   std::size_t low{0}, count{provenanceMap_.size()};
   while (count > 1) {
     std::size_t mid{low + (count >> 1)};