diff --git a/test/Utils/update-verify-tests/expansion.swift b/test/Utils/update-verify-tests/expansion.swift
index 82d0b7318c2..bb29d80fc37 100644
--- a/test/Utils/update-verify-tests/expansion.swift
+++ b/test/Utils/update-verify-tests/expansion.swift
@@ -42,6 +42,11 @@
 // RUN: not %target-swift-frontend-verify -I %t -plugin-path %swift-plugin-dir -typecheck %t/unparsed.swift 2>%t/output.txt -Rmacro-expansions
 // RUN: not %update-verify-tests < %t/output.txt | %FileCheck --check-prefix CHECK-UNPARSED %s
 
+// RUN: not %target-swift-frontend-verify -load-plugin-library %t/%target-library-name(UnstringifyMacroDefinition) -typecheck %t/escaped.swift 2>%t/output.txt -Rmacro-expansions
+// RUN: %update-verify-tests < %t/output.txt
+// RUN: %target-swift-frontend-verify -load-plugin-library %t/%target-library-name(UnstringifyMacroDefinition) -typecheck %t/escaped.swift -Rmacro-expansions
+// RUN: %diff %t/escaped.swift %t/escaped.swift.expected
+
 //--- single.swift
 @attached(peer, names: overloaded)
 macro unstringifyPeer(_ s: String) =
@@ -260,3 +265,43 @@ func bar() {
   foo(a, &b)
 }
 
+//--- escaped.swift
+@attached(peer, names: overloaded)
+macro unstringifyPeer(_ s: String) =
+    #externalMacro(module: "UnstringifyMacroDefinition", type: "UnstringifyPeerMacro")
+
+@unstringifyPeer("""
+func foo(_ x: Int) {
+    let a = "\\(x)"
+    let b = "\\(x)"
+}
+""")
+// NB: DiagnosticVerifier interprets "\\(x)" as "\(x)"
+// expected-expansion@+3:30{{
+//   expected-remark@2{{macro content: |let a = "\\(x)"|}}
+// }}
+func foo() { let _ = "\(2)" }
+
+//--- escaped.swift.expected
+@attached(peer, names: overloaded)
+macro unstringifyPeer(_ s: String) =
+    #externalMacro(module: "UnstringifyMacroDefinition", type: "UnstringifyPeerMacro")
+
+// expected-note@+1 6{{in expansion of macro 'unstringifyPeer' on global function 'foo()' here}}
+@unstringifyPeer("""
+func foo(_ x: Int) {
+    let a = "\\(x)"
+    let b = "\\(x)"
+}
+""")
+// NB: DiagnosticVerifier interprets "\\(x)" as "\(x)"
+// expected-expansion@+8:30{{
+//   expected-remark@1{{macro content: |func foo(_ x: Int) {|}}
+//   expected-warning@2{{initialization of immutable value 'a' was never used; consider replacing with assignment to '_' or removing it}}
+//   expected-remark@2{{macro content: |    let a = "\\(x)"|}}
+//   expected-warning@3{{initialization of immutable value 'b' was never used; consider replacing with assignment to '_' or removing it}}
+//   expected-remark@3{{macro content: |    let b = "\\(x)"|}}
+//   expected-remark@4{{macro content: |}|}}
+// }}
+func foo() { let _ = "\(2)" }
+
diff --git a/utils/update_verify_tests/core.py b/utils/update_verify_tests/core.py
index 79d6325bb0b..fe636deb4e3 100644
--- a/utils/update_verify_tests/core.py
+++ b/utils/update_verify_tests/core.py
@@ -1,5 +1,6 @@
 import sys
 import re
+from codecs import encode, decode
 
 DEBUG = False
 
@@ -172,7 +173,9 @@ class Diag:
         if self.category == "expansion":
             return base_s + "{{"
         else:
-            return base_s + "{{" + self.diag_content + "}}"
+            # python trivia: raw strings can't end with a backslash
+            escaped_diag_s = self.diag_content.replace("\\", "\\\\")
+            return base_s + "{{" + escaped_diag_s + "}}"
 
 
 class ExpansionDiagClose:
@@ -245,9 +248,12 @@ def parse_diag(line, filename, prefix):
     count = int(count_s) if count_s else 1
     line.content = matched_re.sub("{{DIAG}}", s)
 
+    unescaped_diag_s = decode(
+        encode(diag_s, "utf-8", "backslashreplace"), "unicode-escape"
+    )
     return Diag(
         check_prefix,
-        diag_s,
+        unescaped_diag_s,
         category_s,
         target_line_n,
         is_absolute,