diff --git a/clang/lib/Format/Format.cpp b/clang/lib/Format/Format.cpp
index bdaf264e9adce..d7e4d6bb63aeb 100644
--- a/clang/lib/Format/Format.cpp
+++ b/clang/lib/Format/Format.cpp
@@ -4052,6 +4052,7 @@ LangOptions getFormattingLangOpts(const FormatStyle &Style) {
   // the sequence "<::" will be unconditionally treated as "[:".
   // Cf. Lexer::LexTokenInternal.
   LangOpts.Digraphs = SinceCpp11;
+  LangOpts.Trigraphs = Style.isCpp();
 
   LangOpts.LineComment = 1;
   LangOpts.Bool = 1;
diff --git a/clang/lib/Format/FormatTokenLexer.cpp b/clang/lib/Format/FormatTokenLexer.cpp
index 06f68ec8b0fc1..f9442265a8e59 100644
--- a/clang/lib/Format/FormatTokenLexer.cpp
+++ b/clang/lib/Format/FormatTokenLexer.cpp
@@ -1220,12 +1220,11 @@ static size_t countLeadingWhitespace(StringRef Text) {
         break;
       // Splice found, consume it.
       Cur = Lookahead + 1;
-    } else if (Cur[0] == '?' && Cur[1] == '?' && Cur[2] == '/' &&
-               (Cur[3] == '\n' || Cur[3] == '\r')) {
+    } else if (End - Cur >= 4u && Cur[0] == '?' && Cur[1] == '?' &&
+               Cur[2] == '/' && (Cur[3] == '\n' || Cur[3] == '\r')) {
       // Newlines can also be escaped by a '?' '?' '/' trigraph. By the way, the
       // characters are quoted individually in this comment because if we write
       // them together some compilers warn that we have a trigraph in the code.
-      assert(End - Cur >= 4);
       Cur += 4;
     } else {
       break;
@@ -1300,8 +1299,11 @@ FormatToken *FormatTokenLexer::getNextToken() {
       case '\\':
       case '?':
       case '/':
-        // The text was entirely whitespace when this loop was entered. Thus
-        // this has to be an escape sequence.
+        // The code preceding the loop and in the countLeadingWhitespace
+        // function guarantees that Text is entirely whitespace, not including
+        // comments but including escaped newlines which may be escaped with a
+        // trigraph. So if 1 of these characters show up, then it has to be in
+        // an escape sequence.
         assert(Text.substr(i, 4) == "\?\?/\r" ||
                Text.substr(i, 4) == "\?\?/\n" ||
                (i >= 1 && (Text.substr(i - 1, 4) == "\?\?/\r" ||
diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index 944e7c3fb152a..40b85f0dad355 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -6681,6 +6681,31 @@ TEST_F(FormatTest, EscapedNewlines) {
                "  int x(int a);",
                AlignLeft);
 
+  // Escaped with a trigraph.
+  verifyFormat("#define A \\\n"
+               "  int i;  \\\n"
+               "  int j;",
+               "#define A \?\?/\n"
+               "int i;\?\?/\n"
+               "  int j;",
+               Narrow);
+  verifyFormat("#define A \\\r\n"
+               "  int i;  \\\r\n"
+               "  int j;",
+               "#define A \?\?/\r\n"
+               "int i;\?\?/\r\n"
+               "  int j;",
+               Narrow);
+  verifyFormat("#define A int i;", "#define A \?\?/\n"
+                                   "int i;");
+  verifyFormat("#define A int i;", "#define A \?\?/\r\n"
+                                   "int i;");
+  // In a language that does not support the trigraph, the program should not
+  // crash.
+  verifyNoCrash("#define A \?\?/\n"
+                "int i;",
+                getGoogleStyle(FormatStyle::LK_CSharp));
+
   // CRLF line endings
   verifyFormat("#define A \\\r\n  int i;  \\\r\n  int j;",
                "#define A \\\r\nint i;\\\r\n  int j;", Narrow);