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
@@ -308,7 +308,7 @@
           // Find the last line with lower level.
           auto J = I - 1;
           for (; J != AnnotatedLines.begin(); --J)
-            if ((*J)->Level < TheLine->Level)
+            if (!(*J)->InPPDirective && (*J)->Level < TheLine->Level)
               break;
           if ((*J)->Level >= TheLine->Level)
             return false;
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
@@ -12766,6 +12766,13 @@
                "};",
                MergeInlineOnly);
 
+  verifyFormat("class C {\n"
+               "#ifdef A\n"
+               "  int f() { return 42; }\n"
+               "#endif\n"
+               "};",
+               MergeInlineOnly);
+
   // Also verify behavior when BraceWrapping.AfterFunction = true
   MergeInlineOnly.BreakBeforeBraces = FormatStyle::BS_Custom;
   MergeInlineOnly.BraceWrapping.AfterFunction = true;