diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
index 2cc7f21bf60c4..1e5734c9c834e 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -3195,6 +3195,10 @@ uint64_t ASTWriter::WriteDeclContextLexicalBlock(ASTContext &Context,
   if (DC->decls_empty())
     return 0;
 
+  // In reduced BMI, we don't care the declarations in functions.
+  if (GeneratingReducedBMI && DC->isFunctionOrMethod())
+    return 0;
+
   uint64_t Offset = Stream.GetCurrentBitNo();
   SmallVector<uint32_t, 128> KindDeclPairs;
   for (const auto *D : DC->decls()) {
diff --git a/clang/test/Modules/no-local-decl-in-reduced-bmi.cppm b/clang/test/Modules/no-local-decl-in-reduced-bmi.cppm
new file mode 100644
index 0000000000000..41ae2bf0dec80
--- /dev/null
+++ b/clang/test/Modules/no-local-decl-in-reduced-bmi.cppm
@@ -0,0 +1,33 @@
+// Test that we won't record local declarations by default in reduced BMI.
+
+// RUN: rm -rf %t
+// RUN: split-file %s %t
+// RUN: cd %t
+//
+// RUN: %clang_cc1 -std=c++20 %t/a.cppm -emit-reduced-module-interface -o %t/a.pcm
+// RUN: llvm-bcanalyzer --dump --disable-histogram --show-binary-blobs %t/a.pcm > %t/a.dump
+// RUN: cat %t/a.dump | FileCheck %t/a.cppm
+//
+// RUN: %clang_cc1 -std=c++20 %t/b.cppm -emit-reduced-module-interface -o %t/b.pcm
+// RUN: llvm-bcanalyzer --dump --disable-histogram --show-binary-blobs %t/b.pcm > %t/b.dump
+// RUN: cat %t/b.dump | FileCheck %t/b.cppm
+
+//--- a.cppm
+export module a;
+export int func() {
+    int v = 43;
+    return 43;
+}
+
+// Test that the variable declaration is not recorded completely.
+// CHECK-NOT: <DECL_VAR
+
+//--- b.cppm
+export module b;
+export inline int func() {
+    int v = 43;
+    return v;
+}
+
+// Check that we still records the declaration from inline functions.
+// CHECK: <DECL_VAR