2 files changed, 6 insertions, 1 deletions
diff --git a/absl/types/span.h b/absl/types/span.h
index 3283145a56b4..25347c63fe8c 100644
--- a/absl/types/span.h
+++ b/absl/types/span.h
@@ -276,7 +276,7 @@ class Span {
   // Returns a reference to the i'th element of this span.
   constexpr reference operator[](size_type i) const noexcept {
     // MSVC 2015 accepts this as constexpr, but not ptr_[i]
-    return *(data() + i);
+    return ABSL_ASSERT(i < size()), *(data() + i);
   }
 
   // Span::at()
diff --git a/absl/types/span_test.cc b/absl/types/span_test.cc
index 22467a0a767e..6ac234d365ad 100644
--- a/absl/types/span_test.cc
+++ b/absl/types/span_test.cc
@@ -232,6 +232,11 @@ TEST(IntSpan, ElementAccess) {
 
   EXPECT_EQ(s.front(), s[0]);
   EXPECT_EQ(s.back(), s[9]);
+
+#ifndef NDEBUG
+  EXPECT_DEATH_IF_SUPPORTED(s[-1], "");
+  EXPECT_DEATH_IF_SUPPORTED(s[10], "");
+#endif
 }
 
 TEST(IntSpan, AtThrows) {