diff --git a/clang/lib/Format/TokenAnnotator.cpp b/clang/lib/Format/TokenAnnotator.cpp
--- a/clang/lib/Format/TokenAnnotator.cpp
+++ b/clang/lib/Format/TokenAnnotator.cpp
@@ -3294,6 +3294,11 @@
     return Right.WhitespaceRange.getBegin() != Right.WhitespaceRange.getEnd();
   };
 
+  // If the token is finalized don't touch it (as it could be in a
+  // clang-format-off section).
+  if (Left.Finalized)
+    return HasExistingWhitespace();
+
   if (Right.Tok.getIdentifierInfo() && Left.Tok.getIdentifierInfo())
     return true; // Never ever merge two identifiers.
 
diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -21156,6 +21156,16 @@
   verifyFormat("A< A< int > >();", Spaces);
   verifyFormat("A<A<int > >();", Spaces);
   verifyFormat("A< A< int>>();", Spaces);
+
+  Spaces.SpacesInAngles = FormatStyle::SIAS_Always;
+  verifyFormat("// clang-format off\n"
+               "foo<<<1, 1>>>();\n"
+               "// clang-format on\n",
+               Spaces);
+  verifyFormat("// clang-format off\n"
+               "foo< < <1, 1> > >();\n"
+               "// clang-format on\n",
+               Spaces);
 }
 
 TEST_F(FormatTest, SpaceAfterTemplateKeyword) {