diff --git a/toolchain/check/context.cpp b/toolchain/check/context.cpp
index a03880ca338f..2bf0e5fd94ab 100644
--- a/toolchain/check/context.cpp
+++ b/toolchain/check/context.cpp
@@ -137,13 +137,13 @@ auto Context::ReplaceInstBeforeConstantUse(
   constant_values().Set(inst_id, const_id);
 }
 
-auto Context::DiagnoseDuplicateName(Parse::NodeId parse_node,
+auto Context::DiagnoseDuplicateName(SemIR::InstId dup_def_id,
                                     SemIR::InstId prev_def_id) -> void {
   CARBON_DIAGNOSTIC(NameDeclDuplicate, Error,
                     "Duplicate name being declared in the same scope.");
   CARBON_DIAGNOSTIC(NameDeclPrevious, Note,
                     "Name is previously declared here.");
-  emitter_->Build(parse_node, NameDeclDuplicate)
+  emitter_->Build(dup_def_id, NameDeclDuplicate)
       .Note(prev_def_id, NameDeclPrevious)
       .Emit();
 }
@@ -195,7 +195,7 @@ auto Context::AddPackageImports(Parse::NodeId import_node,
 
   // Add the import to lookup. Should always succeed because imports will be
   // uniquely named.
-  AddNameToLookup(import_node, name_id, inst_id);
+  AddNameToLookup(name_id, inst_id);
   // Add a name for formatted output. This isn't used in name lookup in order
   // to reduce indirection, but it's separate from the Import because it
   // otherwise fits in an Inst.
@@ -206,8 +206,8 @@ auto Context::AddPackageImports(Parse::NodeId import_node,
                                         .value_id = inst_id}});
 }
 
-auto Context::AddNameToLookup(Parse::NodeId name_node, SemIR::NameId name_id,
-                              SemIR::InstId target_id) -> void {
+auto Context::AddNameToLookup(SemIR::NameId name_id, SemIR::InstId target_id)
+    -> void {
   if (current_scope().names.insert(name_id).second) {
     // TODO: Reject if we previously performed a failed lookup for this name in
     // this scope or a scope nested within it.
@@ -218,7 +218,7 @@ auto Context::AddNameToLookup(Parse::NodeId name_node, SemIR::NameId name_id,
     lexical_results.push_back(
         {.inst_id = target_id, .scope_index = current_scope_index()});
   } else {
-    DiagnoseDuplicateName(name_node,
+    DiagnoseDuplicateName(target_id,
                           lexical_lookup_.Get(name_id).back().inst_id);
   }
 }
diff --git a/toolchain/check/context.h b/toolchain/check/context.h
index b98bdfacf172..c3a9f407343a 100644
--- a/toolchain/check/context.h
+++ b/toolchain/check/context.h
@@ -121,8 +121,7 @@ class Context {
                          bool has_load_error) -> void;
 
   // Adds a name to name lookup. Prints a diagnostic for name conflicts.
-  auto AddNameToLookup(Parse::NodeId name_node, SemIR::NameId name_id,
-                       SemIR::InstId target_id) -> void;
+  auto AddNameToLookup(SemIR::NameId name_id, SemIR::InstId target_id) -> void;
 
   // Performs name lookup in a specified scope for a name appearing in a
   // declaration, returning the referenced instruction. If scope_id is invalid,
@@ -147,7 +146,7 @@ class Context {
       -> SemIR::InstId;
 
   // Prints a diagnostic for a duplicate name.
-  auto DiagnoseDuplicateName(Parse::NodeId parse_node,
+  auto DiagnoseDuplicateName(SemIR::InstId dup_def_id,
                              SemIR::InstId prev_def_id) -> void;
 
   // Prints a diagnostic for a missing name.
diff --git a/toolchain/check/decl_name_stack.cpp b/toolchain/check/decl_name_stack.cpp
index 74639bda3124..d9b64d8cc011 100644
--- a/toolchain/check/decl_name_stack.cpp
+++ b/toolchain/check/decl_name_stack.cpp
@@ -67,8 +67,7 @@ auto DeclNameStack::LookupOrAddName(NameContext name_context,
 
     case NameContext::State::Unresolved:
       if (!name_context.target_scope_id.is_valid()) {
-        context_->AddNameToLookup(name_context.parse_node,
-                                  name_context.unresolved_name_id, target_id);
+        context_->AddNameToLookup(name_context.unresolved_name_id, target_id);
       } else {
         auto& name_scope =
             context_->name_scopes().Get(name_context.target_scope_id);
@@ -103,7 +102,7 @@ auto DeclNameStack::AddNameToLookup(NameContext name_context,
                                     SemIR::InstId target_id) -> void {
   auto existing_inst_id = LookupOrAddName(name_context, target_id);
   if (existing_inst_id.is_valid()) {
-    context_->DiagnoseDuplicateName(name_context.parse_node, existing_inst_id);
+    context_->DiagnoseDuplicateName(target_id, existing_inst_id);
   }
 }
 
diff --git a/toolchain/check/handle_class.cpp b/toolchain/check/handle_class.cpp
index 30c385a3d48f..50529482da2c 100644
--- a/toolchain/check/handle_class.cpp
+++ b/toolchain/check/handle_class.cpp
@@ -85,7 +85,7 @@ static auto BuildClassDecl(Context& context, Parse::AnyClassDeclId parse_node)
       // declaration.
     } else {
       // This is a redeclaration of something other than a class.
-      context.DiagnoseDuplicateName(name_context.parse_node, existing_id);
+      context.DiagnoseDuplicateName(class_decl_id, existing_id);
     }
   }
 
@@ -149,7 +149,7 @@ auto HandleClassDefinitionStart(Context& context,
   context.PushScope(class_decl_id, class_info.scope_id);
 
   // Introduce `Self`.
-  context.AddNameToLookup(parse_node, SemIR::NameId::SelfType,
+  context.AddNameToLookup(SemIR::NameId::SelfType,
                           context.types().GetInstId(class_info.self_type_id));
 
   context.inst_block_stack().Push();
diff --git a/toolchain/check/handle_function.cpp b/toolchain/check/handle_function.cpp
index 530fdf50d320..0fab886d87fb 100644
--- a/toolchain/check/handle_function.cpp
+++ b/toolchain/check/handle_function.cpp
@@ -164,7 +164,7 @@ static auto BuildFunctionDecl(Context& context,
       }
     } else {
       // This is a redeclaration of something other than a function.
-      context.DiagnoseDuplicateName(name_context.parse_node, existing_id);
+      context.DiagnoseDuplicateName(function_decl_id, existing_id);
     }
   }
 
@@ -264,7 +264,6 @@ auto HandleFunctionDefinitionStart(Context& context,
 
     if (auto fn_param = param.TryAs<SemIR::AnyBindName>()) {
       context.AddNameToLookup(
-          context.insts().GetParseNode(param_id),
           context.bind_names().Get(fn_param->bind_name_id).name_id, param_id);
     } else {
       CARBON_FATAL() << "Unexpected kind of parameter in function definition "
diff --git a/toolchain/check/handle_interface.cpp b/toolchain/check/handle_interface.cpp
index 6f3a6df33c7b..0272574f26fe 100644
--- a/toolchain/check/handle_interface.cpp
+++ b/toolchain/check/handle_interface.cpp
@@ -68,7 +68,7 @@ static auto BuildInterfaceDecl(Context& context,
       // declaration.
     } else {
       // This is a redeclaration of something other than a interface.
-      context.DiagnoseDuplicateName(name_context.parse_node, existing_id);
+      context.DiagnoseDuplicateName(interface_decl_id, existing_id);
     }
   }
 
diff --git a/toolchain/check/handle_let.cpp b/toolchain/check/handle_let.cpp
index 93d55deb6045..5eba08dd2632 100644
--- a/toolchain/check/handle_let.cpp
+++ b/toolchain/check/handle_let.cpp
@@ -66,8 +66,7 @@ auto HandleLetDecl(Context& context, Parse::LetDeclId parse_node) -> bool {
 
   // Add the name of the binding to the current scope.
   auto name_id = context.bind_names().Get(bind_name.bind_name_id).name_id;
-  context.AddNameToLookup(context.insts().GetParseNode(pattern_id), name_id,
-                          pattern_id);
+  context.AddNameToLookup(name_id, pattern_id);
   return true;
 }
 
diff --git a/toolchain/check/testdata/interface/fail_duplicate.carbon b/toolchain/check/testdata/interface/fail_duplicate.carbon
index fa9f26e2862b..3d581b7c70ef 100644
--- a/toolchain/check/testdata/interface/fail_duplicate.carbon
+++ b/toolchain/check/testdata/interface/fail_duplicate.carbon
@@ -18,9 +18,9 @@ interface Interface {
 
 fn Function();
 
-// CHECK:STDERR: fail_duplicate.carbon:[[@LINE+6]]:11: ERROR: Duplicate name being declared in the same scope.
+// CHECK:STDERR: fail_duplicate.carbon:[[@LINE+6]]:1: ERROR: Duplicate name being declared in the same scope.
 // CHECK:STDERR: interface Function;
-// CHECK:STDERR:           ^~~~~~~~
+// CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~
 // CHECK:STDERR: fail_duplicate.carbon:[[@LINE-5]]:1: Name is previously declared here.
 // CHECK:STDERR: fn Function();
 // CHECK:STDERR: ^~~~~~~~~~~~~~
@@ -28,9 +28,9 @@ interface Function;
 
 class Class;
 
-// CHECK:STDERR: fail_duplicate.carbon:[[@LINE+6]]:11: ERROR: Duplicate name being declared in the same scope.
+// CHECK:STDERR: fail_duplicate.carbon:[[@LINE+6]]:1: ERROR: Duplicate name being declared in the same scope.
 // CHECK:STDERR: interface Class { }
-// CHECK:STDERR:           ^~~~~
+// CHECK:STDERR: ^~~~~~~~~~~~~~~~~
 // CHECK:STDERR: fail_duplicate.carbon:[[@LINE-5]]:1: Name is previously declared here.
 // CHECK:STDERR: class Class;
 // CHECK:STDERR: ^~~~~~~~~~~~
diff --git a/toolchain/check/testdata/namespace/fail_import_of_repeat.carbon b/toolchain/check/testdata/namespace/fail_import_of_repeat.carbon
index c8bf91812146..227379ec1206 100644
--- a/toolchain/check/testdata/namespace/fail_import_of_repeat.carbon
+++ b/toolchain/check/testdata/namespace/fail_import_of_repeat.carbon
@@ -9,9 +9,9 @@
 package Implicit api;
 
 namespace NS;
-// CHECK:STDERR: implicit.carbon:[[@LINE+6]]:11: ERROR: Duplicate name being declared in the same scope.
+// CHECK:STDERR: implicit.carbon:[[@LINE+6]]:1: ERROR: Duplicate name being declared in the same scope.
 // CHECK:STDERR: namespace NS;
-// CHECK:STDERR:           ^~
+// CHECK:STDERR: ^~~~~~~~~~~~~
 // CHECK:STDERR: implicit.carbon:[[@LINE-4]]:1: Name is previously declared here.
 // CHECK:STDERR: namespace NS;
 // CHECK:STDERR: ^~~~~~~~~~~~~