diff --git a/clang/lib/Sema/SemaOverload.cpp b/clang/lib/Sema/SemaOverload.cpp
--- a/clang/lib/Sema/SemaOverload.cpp
+++ b/clang/lib/Sema/SemaOverload.cpp
@@ -420,7 +420,7 @@
   //    value when converted back to the original type.
   case ICK_Integral_Conversion:
   IntegralConversion: {
-    assert(FromType->isIntegralOrUnscopedEnumerationType());
+    assert(FromType->isIntegralOrEnumerationType());
     assert(ToType->isIntegralOrUnscopedEnumerationType());
     const bool FromSigned = FromType->isSignedIntegerOrEnumerationType();
     const unsigned FromWidth = Ctx.getIntWidth(FromType);
diff --git a/clang/test/SemaCXX/cxx17-enum-scoped.cpp b/clang/test/SemaCXX/cxx17-enum-scoped.cpp
new file mode 100644
--- /dev/null
+++ b/clang/test/SemaCXX/cxx17-enum-scoped.cpp
@@ -0,0 +1,9 @@
+// RUN: %clang_cc1 -fsyntax-only -pedantic -std=c++17 -verify -triple x86_64-apple-darwin %s
+
+// expected-no-diagnostics
+
+namespace PR54158 {
+  enum class A : int;
+  enum class B : int;
+  B x{A{}};
+}