diff --git a/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.virtuals/overflow.pass.cpp b/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.virtuals/overflow.pass.cpp
index 990f918ce51f..6aedd8388f00 100644
--- a/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.virtuals/overflow.pass.cpp
+++ b/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.virtuals/overflow.pass.cpp
@@ -38,7 +38,7 @@ struct testbuf
 
 int main(int, char**)
 {
-    // sanity check
+    // check overflow
     {
         testbuf<char> tb("");
         tb.overflow();
diff --git a/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.virtuals/pbackfail.pass.cpp b/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.virtuals/pbackfail.pass.cpp
index 9a7d30e1e214..fb326022c631 100644
--- a/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.virtuals/pbackfail.pass.cpp
+++ b/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.virtuals/pbackfail.pass.cpp
@@ -36,7 +36,7 @@ struct testbuf
 
 int main(int, char**)
 {
-    // sanity check
+    // check pbackfail
     {
         testbuf<char> tb("");
         tb.pbackfail();