diff --git a/clang/lib/Sema/SemaLambda.cpp b/clang/lib/Sema/SemaLambda.cpp
index e74fe02bd0cf5..f7fd1d1831500 100644
--- a/clang/lib/Sema/SemaLambda.cpp
+++ b/clang/lib/Sema/SemaLambda.cpp
@@ -304,12 +304,24 @@ Sema::getCurrentMangleNumberContext(const DeclContext *DC) {
     //    Yeah, I think the only cases left where lambdas don't need a
     //    mangling are when they have (effectively) internal linkage or appear
     //    in a non-inline function in a non-module translation unit.
-    if (auto *ND = dyn_cast<NamedDecl>(ManglingContextDecl ? ManglingContextDecl
-                                                           : cast<Decl>(DC));
+
+    Decl *ManglingContextDeclForModule = [&]() {
+      if (!ManglingContextDecl || [&]() {
+            // If we must allocate mangling numbers but the
+            // `ManglingContextDecl` is a local variable, use the `DeclContext`
+            // containing the lambda expression instead.
+            VarDecl *Var = dyn_cast<VarDecl>(ManglingContextDecl);
+            return Var && Var->isLocalVarDecl();
+          }())
+        return const_cast<Decl *>(cast<Decl>(DC));
+
+      return ManglingContextDecl;
+    }();
+
+    if (auto *ND = dyn_cast<NamedDecl>(ManglingContextDeclForModule);
         ND && (ND->isInNamedModule() || ND->isFromGlobalModule()) &&
         ND->isExternallyVisible()) {
-      if (!ManglingContextDecl)
-        ManglingContextDecl = const_cast<Decl *>(cast<Decl>(DC));
+      ManglingContextDecl = ND;
       return NonInlineInModulePurview;
     }
 
diff --git a/clang/test/Modules/pr178893.cppm b/clang/test/Modules/pr178893.cppm
new file mode 100644
index 0000000000000..6d2a599588667
--- /dev/null
+++ b/clang/test/Modules/pr178893.cppm
@@ -0,0 +1,29 @@
+// RUN: %clang_cc1 -std=c++20 -triple x86_64-apple-macosx10.7.0 -fmodules -xc++ -emit-llvm -o - %s -w | FileCheck %s
+
+// CHECK-LABEL: define linkonce_odr noundef i32 @_ZZN8PR178893W3mod6format5parseEPiENKUlvE_clEv
+// CHECK-LABEL: define linkonce_odr noundef i32 @_ZZN8PR178893W3mod6format5parseEPiENKUlvE0_clEv
+
+export module mod;
+
+namespace PR178893 {
+  struct format {
+      static inline int parse(int* i)
+      {
+          int number;
+          number = [&]() -> int { return i[0]; }();
+
+          volatile bool b = true;
+          if (b) {
+              auto identifier = [&]() -> int { return i[1]; }();
+              return identifier;
+          }
+
+          return number;
+      }
+  };
+
+  int test_format() {
+      int n[2] = {1, 0};
+      return format::parse(n);
+  }
+}