diff --git a/clang/lib/Format/UnwrappedLineFormatter.cpp b/clang/lib/Format/UnwrappedLineFormatter.cpp
--- a/clang/lib/Format/UnwrappedLineFormatter.cpp
+++ b/clang/lib/Format/UnwrappedLineFormatter.cpp
@@ -366,20 +366,28 @@
     // instead of TheLine->First.
 
     if (Style.CompactNamespaces) {
-      if (auto nsToken = TheLine->First->getNamespaceToken()) {
-        int i = 0;
-        unsigned closingLine = TheLine->MatchingClosingBlockLineIndex - 1;
-        for (; I + 1 + i != E &&
-               nsToken->TokenText == getNamespaceTokenText(I[i + 1]) &&
-               closingLine == I[i + 1]->MatchingClosingBlockLineIndex &&
-               I[i + 1]->Last->TotalLength < Limit;
-             i++, --closingLine) {
-          // No extra indent for compacted namespaces.
-          IndentTracker.skipLine(*I[i + 1]);
+      if (auto *nsToken = TheLine->First->getNamespaceToken()) {
+        int j = 1;
+        unsigned closingLineIndex = TheLine->MatchingClosingBlockLineIndex - 1;
 
-          Limit -= I[i + 1]->Last->TotalLength;
+        for (; I + j != E &&
+               nsToken->TokenText == getNamespaceTokenText(I[j]) &&
+               closingLineIndex == I[j]->MatchingClosingBlockLineIndex &&
+               I[j]->Last->TotalLength < Limit;
+             j++, --closingLineIndex) {
+          Limit -= I[j]->Last->TotalLength;
+
+          // Reduce indent level for bodies of namespaces which were compacted,
+          // but only if their content was indented in the first place
+          auto *closingLine = AnnotatedLines.begin() + closingLineIndex + 1;
+          auto dedentBy = I[j]->Level - TheLine->Level;
+          for (auto *compactedLine = I + j; compactedLine <= closingLine;
+               compactedLine++) {
+            if (!(*compactedLine)->InPPDirective)
+              (*compactedLine)->Level-= dedentBy;
+          }
         }
-        return i;
+        return j - 1;
       }
 
       if (auto nsToken = getMatchingNamespaceToken(TheLine, AnnotatedLines)) {
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
@@ -4431,6 +4431,24 @@
                    "int k; }} // namespace out::mid",
                    Style));
 
+  verifyFormat("namespace A { namespace B { namespace C {\n"
+               "  int i;\n"
+               "}}} // namespace A::B::C\n"
+               "int main() {\n"
+               "  if (true)\n"
+               "    return 0;\n"
+               "}",
+               "namespace A { namespace B {\n"
+               "namespace C {\n"
+               "  int i;\n"
+               "}} // namespace B::C\n"
+               "} // namespace A\n"
+               "int main() {\n"
+               "  if (true)\n"
+               "    return 0;\n"
+               "}",
+               Style);
+
   Style.NamespaceIndentation = FormatStyle::NI_Inner;
   EXPECT_EQ("namespace out { namespace in {\n"
             "  int i;\n"