diff --git a/clang/lib/CIR/CodeGen/CIRGenExprComplex.cpp b/clang/lib/CIR/CodeGen/CIRGenExprComplex.cpp
index fcde4875393cd..d8f4943a7755a 100644
--- a/clang/lib/CIR/CodeGen/CIRGenExprComplex.cpp
+++ b/clang/lib/CIR/CodeGen/CIRGenExprComplex.cpp
@@ -196,9 +196,8 @@ class ComplexExprEmitter : public StmtVisitor<ComplexExprEmitter, mlir::Value> {
     return Visit(e->getSubExpr());
   }
   mlir::Value VisitCXXDefaultArgExpr(CXXDefaultArgExpr *dae) {
-    cgf.cgm.errorNYI(dae->getExprLoc(),
-                     "ComplexExprEmitter VisitCXXDefaultArgExpr");
-    return {};
+    CIRGenFunction::CXXDefaultArgExprScope scope(cgf, dae);
+    return Visit(dae->getExpr());
   }
   mlir::Value VisitCXXDefaultInitExpr(CXXDefaultInitExpr *die) {
     CIRGenFunction::CXXDefaultInitExprScope scope(cgf, die);
diff --git a/clang/lib/CIR/CodeGen/CIRGenFunction.h b/clang/lib/CIR/CodeGen/CIRGenFunction.h
index 3c36f5c697118..48218d9aa75f1 100644
--- a/clang/lib/CIR/CodeGen/CIRGenFunction.h
+++ b/clang/lib/CIR/CodeGen/CIRGenFunction.h
@@ -733,6 +733,11 @@ class CIRGenFunction : public CIRGenTypeCache {
     SourceLocExprScopeGuard sourceLocScope;
   };
 
+  struct CXXDefaultArgExprScope : SourceLocExprScopeGuard {
+    CXXDefaultArgExprScope(CIRGenFunction &cfg, const CXXDefaultArgExpr *e)
+        : SourceLocExprScopeGuard(e, cfg.curSourceLocExprScope) {}
+  };
+
   LValue makeNaturalAlignPointeeAddrLValue(mlir::Value v, clang::QualType t);
   LValue makeNaturalAlignAddrLValue(mlir::Value val, QualType ty);
 
diff --git a/clang/test/CIR/CodeGen/complex.cpp b/clang/test/CIR/CodeGen/complex.cpp
index 083d4383e1f7d..55c506bd5f9e9 100644
--- a/clang/test/CIR/CodeGen/complex.cpp
+++ b/clang/test/CIR/CodeGen/complex.cpp
@@ -1405,3 +1405,42 @@ void imag_on_scalar_bool() {
 // OGCG: %[[A_ADDR:.*]] = alloca i8, align 1
 // OGCG: %[[B_ADDR:.*]] = alloca i8, align 1
 // OGCG: store i8 0, ptr %[[B_ADDR]], align 1
+
+void function_with_complex_default_arg(
+    float _Complex a = __builtin_complex(1.0f, 2.2f)) {}
+
+// CIR: %[[ARG_0_ADDR:.*]] = cir.alloca !cir.complex<!cir.float>, !cir.ptr<!cir.complex<!cir.float>>, ["a", init]
+// CIR: cir.store %{{.*}}, %[[ARG_0_ADDR]] : !cir.complex<!cir.float>, !cir.ptr<!cir.complex<!cir.float>>
+
+// TODO(CIR): the difference between the CIR LLVM and OGCG is because the lack of calling convention lowering,
+
+// LLVM: %[[ARG_0_ADDR:.*]] = alloca { float, float }, i64 1, align 4
+// LLVM: store { float, float } %{{.*}}, ptr %[[ARG_0_ADDR]], align 4
+
+// OGCG: %[[ARG_0_ADDR:.*]] = alloca { float, float }, align 4
+// OGCG: store <2 x float> %{{.*}}, ptr %[[ARG_0_ADDR]], align 4
+
+void calling_function_with_default_arg() {
+  function_with_complex_default_arg();
+}
+
+// CIR: %[[DEFAULT_ARG_ADDR:.*]] = cir.alloca !cir.complex<!cir.float>, !cir.ptr<!cir.complex<!cir.float>>, ["coerce"]
+// CIR: %[[DEFAULT_ARG_VAL:.*]] = cir.const #cir.const_complex<#cir.fp<1.000000e+00> : !cir.float, #cir.fp<2.200000e+00> : !cir.float> : !cir.complex<!cir.float>
+// CIR: cir.store{{.*}} %[[DEFAULT_ARG_VAL]], %[[DEFAULT_ARG_ADDR]] : !cir.complex<!cir.float>, !cir.ptr<!cir.complex<!cir.float>>
+// CIR: %[[TMP_DEFAULT_ARG:.*]] = cir.load{{.*}} %[[DEFAULT_ARG_ADDR]] : !cir.ptr<!cir.complex<!cir.float>>, !cir.complex<!cir.float>
+// CIR: cir.call @_Z33function_with_complex_default_argCf(%[[TMP_DEFAULT_ARG]]) : (!cir.complex<!cir.float>) -> ()
+
+// TODO(CIR): the difference between the CIR LLVM and OGCG is because the lack of calling convention lowering,
+
+// LLVM: %[[DEFAULT_ARG_ADDR:.*]] = alloca { float, float }, i64 1, align 4
+// LLVM: store { float, float } { float 1.000000e+00, float 0x40019999A0000000 }, ptr %[[DEFAULT_ARG_ADDR]], align 4
+// LLVM: %[[TMP_DEFAULT_ARG:.*]] = load { float, float }, ptr %[[DEFAULT_ARG_ADDR]], align 4
+// LLVM: call void @_Z33function_with_complex_default_argCf({ float, float } %[[TMP_DEFAULT_ARG]])
+
+// OGCG: %[[DEFAULT_ARG_ADDR:.*]] = alloca { float, float }, align 4
+// OGCG: %[[DEFAULT_ARG_REAL_PTR:.*]] = getelementptr inbounds nuw { float, float }, ptr %[[DEFAULT_ARG_ADDR]], i32 0, i32 0
+// OGCG: %[[DEFAULT_ARG_IMAG_PTR:.*]] = getelementptr inbounds nuw { float, float }, ptr %[[DEFAULT_ARG_ADDR]], i32 0, i32 1
+// OGCG: store float 1.000000e+00, ptr %[[DEFAULT_ARG_REAL_PTR]], align 4
+// OGCG: store float 0x40019999A0000000, ptr %[[DEFAULT_ARG_IMAG_PTR]], align 4
+// OGCG: %[[TMP_DEFAULT_ARG:.*]] = load <2 x float>, ptr %[[DEFAULT_ARG_ADDR]], align 4
+// OGCG: call void @_Z33function_with_complex_default_argCf(<2 x float> {{.*}} %[[TMP_DEFAULT_ARG]])