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
@@ -3339,6 +3339,9 @@
     if (Left.is(tok::ellipsis) && Right.is(tok::identifier) &&
         Line.First->is(Keywords.kw_import))
       return false;
+    // Space in __attribute__((attr)) ::type.
+    if (Left.is(TT_AttributeParen) && Right.is(tok::coloncolon))
+      return true;
 
     if (Left.is(tok::kw_operator))
       return Right.is(tok::coloncolon);
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
@@ -10028,6 +10028,7 @@
   verifyFormat("SomeType s __attribute__((unused)) (InitValue);");
   verifyFormat("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa __attribute__((unused))\n"
                "aaaaaaaaaaaaaaaaaaaaaaa(int i);");
+  verifyFormat("__attribute__((nodebug)) ::qualified_type f();");
   FormatStyle AfterType = getLLVMStyle();
   AfterType.AlwaysBreakAfterReturnType = FormatStyle::RTBS_All;
   verifyFormat("__attribute__((nodebug)) void\n"
@@ -10131,6 +10132,7 @@
   verifyFormat("class [[nodiscard]] f {\npublic:\n  f() {}\n}");
   verifyFormat("class [[deprecated(\"so sorry\")]] f {\npublic:\n  f() {}\n}");
   verifyFormat("class [[gnu::unused]] f {\npublic:\n  f() {}\n}");
+  verifyFormat("[[nodiscard]] ::qualified_type f();");
 
   // Make sure we do not mistake attributes for array subscripts.
   verifyFormat("int a() {}\n"