diff --git a/clang/lib/CodeGen/CGExprScalar.cpp b/clang/lib/CodeGen/CGExprScalar.cpp
--- a/clang/lib/CodeGen/CGExprScalar.cpp
+++ b/clang/lib/CodeGen/CGExprScalar.cpp
@@ -463,7 +463,10 @@
     return llvm::ConstantInt::get(ConvertType(E->getType()), E->getValue());
   }
   Value *VisitCXXScalarValueInitExpr(const CXXScalarValueInitExpr *E) {
-    return EmitNullValue(E->getType());
+    // [expr.type.conv]: if the type is cv void and the initializer is () or {},
+    // the expression is a prvalue of type void that performs no initialization.
+    QualType T = E->getType();
+    return T->isVoidType() ? nullptr : EmitNullValue(T);
   }
   Value *VisitGNUNullExpr(const GNUNullExpr *E) {
     return EmitNullValue(E->getType());
diff --git a/clang/test/CodeGenCXX/value-init.cpp b/clang/test/CodeGenCXX/value-init.cpp
--- a/clang/test/CodeGenCXX/value-init.cpp
+++ b/clang/test/CodeGenCXX/value-init.cpp
@@ -338,4 +338,12 @@
   struct optional : optional_data_dtor_base, optional_assign_base {};
   optional f(optional a) { return {optional(a)}; }
 }
+
+namespace PR48889 {
+  // Just make sure we don't hit an assertion, the IR is otherwise unchanged.
+  constexpr void f() {}
+  void g(bool b) {
+    return b ? f() : void();
+  }
+}
 #endif