diff --git a/clang/lib/Format/Format.cpp b/clang/lib/Format/Format.cpp
--- a/clang/lib/Format/Format.cpp
+++ b/clang/lib/Format/Format.cpp
@@ -2160,7 +2160,8 @@
   // Deduplicate #includes.
   Indices.erase(std::unique(Indices.begin(), Indices.end(),
                             [&](unsigned LHSI, unsigned RHSI) {
-                              return Includes[LHSI].Text == Includes[RHSI].Text;
+                              return Includes[LHSI].Text.trim() ==
+                                     Includes[RHSI].Text.trim();
                             }),
                 Indices.end());
 
diff --git a/clang/unittests/Format/SortIncludesTest.cpp b/clang/unittests/Format/SortIncludesTest.cpp
--- a/clang/unittests/Format/SortIncludesTest.cpp
+++ b/clang/unittests/Format/SortIncludesTest.cpp
@@ -266,12 +266,19 @@
             sort(" #include \"a.h\"\n"
                  "  #include \"c.h\"\n"
                  "   #include \"b.h\"\n"));
+  EXPECT_EQ("#include \"a.h\"\n", sort("#include \"a.h\"\n"
+                                       " #include \"a.h\"\n"));
+}
+
+TEST_F(SortIncludesTest, TrailingWhitespace) {
   EXPECT_EQ("#include \"a.h\"\n"
             "#include \"b.h\"\n"
             "#include \"c.h\"\n",
-            sort("# include \"a.h\"\n"
-                 "#  include \"c.h\"\n"
-                 "#   include \"b.h\"\n"));
+            sort("#include \"a.h\" \n"
+                 "#include \"c.h\"  \n"
+                 "#include \"b.h\"   \n"));
+  EXPECT_EQ("#include \"a.h\"\n", sort("#include \"a.h\"\n"
+                                       "#include \"a.h\" \n"));
 }
 
 TEST_F(SortIncludesTest, GreaterInComment) {