diff --git a/lib/AST/ASTDemangler.cpp b/lib/AST/ASTDemangler.cpp
index ae667d06a5e9c..d5e6754845ecc 100644
--- a/lib/AST/ASTDemangler.cpp
+++ b/lib/AST/ASTDemangler.cpp
@@ -755,36 +755,53 @@ Type ASTBuilder::createExistentialMetatypeType(
 Type ASTBuilder::createConstrainedExistentialType(
     Type base, ArrayRef<BuiltRequirement> constraints,
     ArrayRef<BuiltInverseRequirement> inverseRequirements) {
-  // FIXME: Generalize to other kinds of bases.
-  if (!base->getAs<ProtocolType>())
-    return Type();
-  auto baseTy = base->castTo<ProtocolType>();
-  auto baseDecl = baseTy->getDecl();
-  llvm::SmallDenseMap<Identifier, Type> cmap;
-  for (const auto &req : constraints) {
-    switch (req.getKind()) {
-    case RequirementKind::SameShape:
-      llvm_unreachable("Same-shape requirement not supported here");
-    case RequirementKind::Conformance:
-    case RequirementKind::Superclass:
-    case RequirementKind::Layout:
-      continue;
+  Type constrainedBase;
+
+  if (auto baseTy = base->getAs<ProtocolType>()) {
+    auto baseDecl = baseTy->getDecl();
+    llvm::SmallDenseMap<Identifier, Type> cmap;
+    for (const auto &req : constraints) {
+      switch (req.getKind()) {
+      case RequirementKind::SameShape:
+        llvm_unreachable("Same-shape requirement not supported here");
+      case RequirementKind::Conformance:
+      case RequirementKind::Superclass:
+      case RequirementKind::Layout:
+        continue;
 
-    case RequirementKind::SameType:
-      if (auto *DMT = req.getFirstType()->getAs<DependentMemberType>())
-        cmap[DMT->getName()] = req.getSecondType();
+      case RequirementKind::SameType:
+        if (auto *DMT = req.getFirstType()->getAs<DependentMemberType>())
+          cmap[DMT->getName()] = req.getSecondType();
+      }
     }
-  }
-  llvm::SmallVector<Type, 4> args;
-  for (auto *assocTy : baseDecl->getPrimaryAssociatedTypes()) {
-    auto argTy = cmap.find(assocTy->getName());
-    if (argTy == cmap.end()) {
-      return Type();
+    llvm::SmallVector<Type, 4> args;
+    for (auto *assocTy : baseDecl->getPrimaryAssociatedTypes()) {
+      auto argTy = cmap.find(assocTy->getName());
+      if (argTy == cmap.end()) {
+        return Type();
+      }
+      args.push_back(argTy->getSecond());
+    }
+
+    // We may not have any arguments because the constrained existential is a
+    // plain protocol with an inverse requirement.
+    if (args.empty()) {
+      constrainedBase =
+          ProtocolType::get(baseDecl, baseTy, base->getASTContext());
+    } else {
+      constrainedBase =
+          ParameterizedProtocolType::get(base->getASTContext(), baseTy, args);
     }
-    args.push_back(argTy->getSecond());
+  } else if (base->isAny()) {
+    // The only other case should be that we got an empty PCT, which is equal to
+    // the Any type. The other constraints should have been encoded in the
+    // existential's generic signature (and arrive as BuiltInverseRequirement).
+    constrainedBase = base;
+  } else {
+    return Type();
   }
-  Type constrainedBase =
-      ParameterizedProtocolType::get(base->getASTContext(), baseTy, args);
+
+  assert(constrainedBase);
 
   // Handle inverse requirements.
   if (!inverseRequirements.empty()) {
diff --git a/test/Interpreter/moveonly_existentials.swift b/test/Interpreter/moveonly_existentials.swift
index 929d7942fa1bb..f3ab9465e8036 100644
--- a/test/Interpreter/moveonly_existentials.swift
+++ b/test/Interpreter/moveonly_existentials.swift
@@ -1,5 +1,5 @@
 // RUN: %empty-directory(%t)
-// RUN: %target-build-swift  %s -o %t/bin
+// RUN: %target-build-swift -g %s -o %t/bin
 // RUN: %target-codesign %t/bin
 // RUN: %target-run %t/bin | %FileCheck %s
 
diff --git a/test/TypeDecoder/constrained_existentials.swift b/test/TypeDecoder/constrained_existentials.swift
index b5f5691d3129b..e84ac363d043a 100644
--- a/test/TypeDecoder/constrained_existentials.swift
+++ b/test/TypeDecoder/constrained_existentials.swift
@@ -5,6 +5,7 @@
 // RUN: %lldb-moduleimport-test %t/constrained_existentials -type-from-mangled=%t/input | %FileCheck %s --match-full-lines
 
 func blackHole(_: Any...) {}
+func blackHole_noncopyable(_: consuming any ~Copyable) {}
 
 protocol BaseProto<A, B> {
   associatedtype A
@@ -43,3 +44,16 @@ do {
 
   blackHole(e0, e1, e2)
 }
+
+protocol NCProto: ~Copyable {}
+struct NC: ~Copyable {}
+struct GenNC<T: ~Copyable>: ~Copyable, NCProto {}
+
+do {
+  let e0: any NCProto & ~Copyable = GenNC<NC>()
+  let e1: any NCProto & ~Copyable = GenNC<String>()
+
+  // FIXME: breaks the MoveChecker (rdar://129885532)
+//   blackHole_noncopyable(consume e0)
+//   blackHole_noncopyable(consume e1)
+}