diff --git a/clang/include/clang/Testing/TestClangConfig.h b/clang/include/clang/Testing/TestClangConfig.h
index 5d6be4f65d0ad..92d5cc3cff994 100644
--- a/clang/include/clang/Testing/TestClangConfig.h
+++ b/clang/include/clang/Testing/TestClangConfig.h
@@ -73,7 +73,7 @@ struct TestClangConfig {
     std::string Result;
     llvm::raw_string_ostream OS(Result);
     OS << "{ Language=" << Language << ", Target=" << Target << " }";
-    return OS.str();
+    return Result;
   }
 
   friend std::ostream &operator<<(std::ostream &OS,
diff --git a/clang/unittests/AST/ASTTraverserTest.cpp b/clang/unittests/AST/ASTTraverserTest.cpp
index d633f90b57d2d..b8eff747e3b50 100644
--- a/clang/unittests/AST/ASTTraverserTest.cpp
+++ b/clang/unittests/AST/ASTTraverserTest.cpp
@@ -111,7 +111,7 @@ template <typename... NodeType> std::string dumpASTString(NodeType &&... N) {
 
   Dumper.Visit(std::forward<NodeType &&>(N)...);
 
-  return OS.str();
+  return Buffer;
 }
 
 template <typename... NodeType>
@@ -126,7 +126,7 @@ std::string dumpASTString(TraversalKind TK, NodeType &&... N) {
 
   Dumper.Visit(std::forward<NodeType &&>(N)...);
 
-  return OS.str();
+  return Buffer;
 }
 
 const FunctionDecl *getFunctionNode(clang::ASTUnit *AST,
diff --git a/clang/unittests/Analysis/MacroExpansionContextTest.cpp b/clang/unittests/Analysis/MacroExpansionContextTest.cpp
index 2e86457d276ca..7cee64c1b9b0c 100644
--- a/clang/unittests/Analysis/MacroExpansionContextTest.cpp
+++ b/clang/unittests/Analysis/MacroExpansionContextTest.cpp
@@ -95,14 +95,14 @@ class MacroExpansionContextTest : public ::testing::Test {
     std::string Buf;
     llvm::raw_string_ostream OS{Buf};
     Ctx.dumpExpandedTextsToStream(OS);
-    return OS.str();
+    return Buf;
   }
 
   static std::string dumpExpansionRanges(const MacroExpansionContext &Ctx) {
     std::string Buf;
     llvm::raw_string_ostream OS{Buf};
     Ctx.dumpExpansionRangesToStream(OS);
-    return OS.str();
+    return Buf;
   }
 };
 
diff --git a/clang/unittests/Tooling/Syntax/TreeTest.cpp b/clang/unittests/Tooling/Syntax/TreeTest.cpp
index 06da4e80156a4..d2acd324b9ca9 100644
--- a/clang/unittests/Tooling/Syntax/TreeTest.cpp
+++ b/clang/unittests/Tooling/Syntax/TreeTest.cpp
@@ -203,7 +203,7 @@ class ListTest : public SyntaxTreeTest {
 
     OS << "]";
 
-    return OS.str();
+    return Storage;
   }
 
   std::string dumpNodes(ArrayRef<Node *> Nodes) {
@@ -218,7 +218,7 @@ class ListTest : public SyntaxTreeTest {
 
     OS << "]";
 
-    return OS.str();
+    return Storage;
   }
 };