diff --git a/lib/Serialization/SerializedModuleLoader.cpp b/lib/Serialization/SerializedModuleLoader.cpp
index a49d08c04d1..a7ecd5bd2a0 100644
--- a/lib/Serialization/SerializedModuleLoader.cpp
+++ b/lib/Serialization/SerializedModuleLoader.cpp
@@ -1723,6 +1723,13 @@ bool MemoryBufferSerializedModuleLoader::unregisterMemoryBuffer(
 
 void SerializedModuleLoaderBase::loadExtensions(NominalTypeDecl *nominal,
                                                 unsigned previousGeneration) {
+  // Nominals in parsed SourceFiles can't have extensions provided by imported
+  // serialized modules. This is necessary to avoid triggering semantic requests
+  // from extension binding since looking up extensions may need to compute the
+  // mangled name.
+  if (nominal->getParentSourceFile())
+    return;
+
   for (auto &modulePair : LoadedModuleFiles) {
     if (modulePair.second <= previousGeneration)
       continue;
diff --git a/test/decl/ext/extension_binding_multiple_nested.swift b/test/decl/ext/extension_binding_multiple_nested.swift
new file mode 100644
index 00000000000..e8cc7fc51d0
--- /dev/null
+++ b/test/decl/ext/extension_binding_multiple_nested.swift
@@ -0,0 +1,40 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-typecheck-verify-swift
+
+// Make sure we can produce a valid interface
+// RUN: %target-swift-emit-module-interface(%t.swiftinterface) %s -module-name Lib
+// RUN: %target-swift-typecheck-module-from-interface(%t.swiftinterface) -module-name Lib
+
+// https://github.com/swiftlang/swift/issues/86285
+public enum A {}
+
+extension A {
+  public struct B<T: A.P> {}
+}
+extension A.B {
+  public struct Set {}
+}
+extension A.B.Set {
+  public struct D {}
+}
+extension A.B.Set.D {
+  public struct E {}
+}
+extension A {
+  public protocol P {}
+}
+
+public enum B {}
+
+extension B {
+  public struct Set<T: A.P> {}
+}
+extension B.Set {
+  public struct X {}
+}
+extension B.Set.X {
+  public struct E {}
+}
+extension B {
+  public protocol P {}
+}
diff --git a/validation-test/IDE/crashers/GenericSignatureImpl-getSuperclassBound-7d168e.swift b/validation-test/IDE/crashers_fixed/GenericSignatureImpl-getSuperclassBound-7d168e.swift
similarity index 55%
rename from validation-test/IDE/crashers/GenericSignatureImpl-getSuperclassBound-7d168e.swift
rename to validation-test/IDE/crashers_fixed/GenericSignatureImpl-getSuperclassBound-7d168e.swift
index d3d2479a7cb..06e99b492fa 100644
--- a/validation-test/IDE/crashers/GenericSignatureImpl-getSuperclassBound-7d168e.swift
+++ b/validation-test/IDE/crashers_fixed/GenericSignatureImpl-getSuperclassBound-7d168e.swift
@@ -1,5 +1,5 @@
 // {"kind":"complete","signature":"swift::GenericSignatureImpl::getSuperclassBound(swift::Type) const"}
-// RUN: not --crash %target-swift-ide-test -code-completion -batch-code-completion -skip-filecheck -code-completion-diagnostics -source-filename %s
+// RUN: %target-swift-ide-test -code-completion -batch-code-completion -skip-filecheck -code-completion-diagnostics -source-filename %s
 protocol a {
   associatedtype b: Error
 }
diff --git a/validation-test/compiler_crashers/ASTMangler-appendExistentialLayout-e5dc06.swift b/validation-test/compiler_crashers_fixed/ASTMangler-appendExistentialLayout-e5dc06.swift
similarity index 85%
rename from validation-test/compiler_crashers/ASTMangler-appendExistentialLayout-e5dc06.swift
rename to validation-test/compiler_crashers_fixed/ASTMangler-appendExistentialLayout-e5dc06.swift
index 297ff1476df..aca7169b86a 100644
--- a/validation-test/compiler_crashers/ASTMangler-appendExistentialLayout-e5dc06.swift
+++ b/validation-test/compiler_crashers_fixed/ASTMangler-appendExistentialLayout-e5dc06.swift
@@ -1,5 +1,5 @@
 // {"kind":"typecheck","signature":"swift::Mangle::ASTMangler::appendExistentialLayout(swift::ExistentialLayout const&, swift::GenericSignature, swift::ValueDecl const*)","stackOverflow":true}
-// RUN: not --crash %target-swift-frontend -typecheck %s
+// RUN: not %target-swift-frontend -typecheck %s
 protocol a {
   typealias b = Int
 }
diff --git a/validation-test/compiler_crashers/ASTMangler-appendExtension-f1419d.swift b/validation-test/compiler_crashers_fixed/ASTMangler-appendExtension-f1419d.swift
similarity index 82%
rename from validation-test/compiler_crashers/ASTMangler-appendExtension-f1419d.swift
rename to validation-test/compiler_crashers_fixed/ASTMangler-appendExtension-f1419d.swift
index 9ee6da3659e..1c7a5b6051d 100644
--- a/validation-test/compiler_crashers/ASTMangler-appendExtension-f1419d.swift
+++ b/validation-test/compiler_crashers_fixed/ASTMangler-appendExtension-f1419d.swift
@@ -1,4 +1,4 @@
 // {"kind":"typecheck","signature":"swift::Mangle::ASTMangler::appendExtension(swift::ExtensionDecl const*, swift::Mangle::ASTMangler::BaseEntitySignature&, llvm::StringRef)","stackOverflow":true}
-// RUN: not --crash %target-swift-frontend -typecheck %s
+// RUN: not %target-swift-frontend -typecheck %s
 extension Collection where Self : a {
   struct Index protocol a
diff --git a/validation-test/compiler_crashers/RequirementMachine-lookupNestedType-18f909.swift b/validation-test/compiler_crashers_fixed/RequirementMachine-lookupNestedType-18f909.swift
similarity index 82%
rename from validation-test/compiler_crashers/RequirementMachine-lookupNestedType-18f909.swift
rename to validation-test/compiler_crashers_fixed/RequirementMachine-lookupNestedType-18f909.swift
index e2c7c5f7084..04eb935ac71 100644
--- a/validation-test/compiler_crashers/RequirementMachine-lookupNestedType-18f909.swift
+++ b/validation-test/compiler_crashers_fixed/RequirementMachine-lookupNestedType-18f909.swift
@@ -1,5 +1,5 @@
 // {"kind":"typecheck","original":"25bd9966","signature":"swift::rewriting::RequirementMachine::lookupNestedType(swift::Type, swift::Identifier) const"}
-// RUN: not --crash %target-swift-frontend -typecheck %s
+// RUN: not %target-swift-frontend -typecheck %s
 protocol a {
   associatedtype b: Error
 }