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
@@ -3893,6 +3893,9 @@
     return true;
 
   if (Style.isCpp()) {
+    // Space between UDL and dot: auto b = 4s .count();
+    if (Right.is(tok::period) && Left.is(tok::numeric_constant))
+      return true;
     // Space between import <iostream>.
     // or import .....;
     if (Left.is(Keywords.kw_import) && Right.isOneOf(tok::less, tok::ellipsis))
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
@@ -25407,6 +25407,11 @@
   verifyFormat("int i;\n", "int i;", Style);
 }
 
+TEST_F(FormatTest, SpaceAfterUDL) {
+  verifyFormat("auto c = (4s).count();");
+  verifyFormat("auto x = 5s .count() == 5;");
+}
+
 } // namespace
 } // namespace format
 } // namespace clang