diff --git a/toolchain/check/check.cpp b/toolchain/check/check.cpp
index d005e6e9946d..25667b66c58c 100644
--- a/toolchain/check/check.cpp
+++ b/toolchain/check/check.cpp
@@ -158,9 +158,12 @@ struct UnitInfo {
   struct PackageImports {
     // Use the constructor so that the SmallVector is only constructed
     // as-needed.
-    explicit PackageImports(Parse::ImportDirectiveId node_id)
-        : node_id(node_id) {}
+    explicit PackageImports(IdentifierId package_id,
+                            Parse::ImportDirectiveId node_id)
+        : package_id(package_id), node_id(node_id) {}
 
+    // The identifier of the imported package.
+    IdentifierId package_id;
     // The first `import` directive in the file, which declared the package's
     // identifier (even if the import failed). Used for associating diagnostics
     // not specific to a single import.
@@ -187,11 +190,14 @@ struct UnitInfo {
   ErrorTrackingDiagnosticConsumer err_tracker;
   DiagnosticEmitter<Parse::NodeLoc> emitter;
 
-  // A map of package names to outgoing imports. If a package includes
-  // unavailable library imports, it has an entry with has_load_error set.
-  // Invalid imports (for example, `import Main;`) aren't added because they
-  // won't add identifiers to name lookup.
-  llvm::DenseMap<IdentifierId, PackageImports> package_imports_map;
+  // List of the outgoing imports. If a package includes unavailable library
+  // imports, it has an entry with has_load_error set. Invalid imports (for
+  // example, `import Main;`) aren't added because they won't add identifiers to
+  // name lookup.
+  llvm::SmallVector<PackageImports> package_imports;
+
+  // A map of the package names to the outgoing imports above.
+  llvm::DenseMap<IdentifierId, int32_t> package_imports_map;
 
   // The remaining number of imports which must be checked before this unit can
   // be processed.
@@ -212,22 +218,25 @@ static auto ImportCurrentPackage(Context& context, UnitInfo& unit_info,
                                  SemIR::InstId package_inst_id,
                                  SemIR::TypeId namespace_type_id) -> void {
   // Add imports from the current package.
-  auto self_import = unit_info.package_imports_map.find(IdentifierId::Invalid);
-  if (self_import == unit_info.package_imports_map.end()) {
+  auto self_import_map_it =
+      unit_info.package_imports_map.find(IdentifierId::Invalid);
+  if (self_import_map_it == unit_info.package_imports_map.end()) {
     // Push the scope; there are no names to add.
     context.scope_stack().Push(package_inst_id, SemIR::NameScopeId::Package);
     return;
   }
+  UnitInfo::PackageImports& self_import =
+      unit_info.package_imports[self_import_map_it->second];
 
   // Track whether an IR was imported in full, including `export import`. This
   // distinguishes from IRs that are indirectly added without all names being
   // exported to this IR.
   llvm::SmallVector<bool> imported_irs(total_ir_count, false);
-  if (self_import->second.has_load_error) {
+  if (self_import.has_load_error) {
     context.name_scopes().Get(SemIR::NameScopeId::Package).has_error = true;
   }
 
-  for (const auto& import : self_import->second.imports) {
+  for (const auto& import : self_import.imports) {
     const auto& import_sem_ir = **import.unit_info->unit->sem_ir;
 
     auto& imported_ir = imported_irs[import_sem_ir.check_ir_id().index];
@@ -288,7 +297,7 @@ static auto InitPackageScopeAndImports(Context& context, UnitInfo& unit_info,
   // First create the constant values map for all imported IRs. We'll populate
   // these with mappings for namespaces as we go.
   size_t num_irs = 0;
-  for (auto& [_, package_imports] : unit_info.package_imports_map) {
+  for (auto& package_imports : unit_info.package_imports) {
     num_irs += package_imports.imports.size();
   }
   if (!unit_info.api_for_impl) {
@@ -334,8 +343,8 @@ static auto InitPackageScopeAndImports(Context& context, UnitInfo& unit_info,
                        namespace_type_id);
   CARBON_CHECK(context.scope_stack().PeekIndex() == ScopeIndex::Package);
 
-  for (auto& [package_id, package_imports] : unit_info.package_imports_map) {
-    if (!package_id.is_valid()) {
+  for (auto& package_imports : unit_info.package_imports) {
+    if (!package_imports.package_id.is_valid()) {
       // Current package is handled above.
       continue;
     }
@@ -348,9 +357,9 @@ static auto InitPackageScopeAndImports(Context& context, UnitInfo& unit_info,
       CARBON_CHECK(!import.names.is_export)
           << "Imports from other packages can't be exported.";
     }
-    ImportLibrariesFromOtherPackage(context, namespace_type_id,
-                                    package_imports.node_id, package_id,
-                                    import_irs, package_imports.has_load_error);
+    ImportLibrariesFromOtherPackage(
+        context, namespace_type_id, package_imports.node_id,
+        package_imports.package_id, import_irs, package_imports.has_load_error);
   }
 }
 
@@ -998,14 +1007,20 @@ static auto TrackImport(
     return;
   }
 
-  // Get the package imports.
-  auto package_imports_it = unit_info.package_imports_map
-                                .try_emplace(import.package_id, import.node_id)
-                                .first;
+  // Get the package imports, or create them if this is the first.
+  auto [package_imports_map_it, is_inserted] =
+      unit_info.package_imports_map.insert(
+          {import.package_id, unit_info.package_imports.size()});
+  if (is_inserted) {
+    unit_info.package_imports.push_back(
+        UnitInfo::PackageImports(import.package_id, import.node_id));
+  }
+  UnitInfo::PackageImports& package_imports =
+      unit_info.package_imports[package_imports_map_it->second];
 
   if (auto api = api_map.find(import_key); api != api_map.end()) {
     // Add references between the file and imported api.
-    package_imports_it->second.imports.push_back({import, api->second});
+    package_imports.imports.push_back({import, api->second});
     ++unit_info.imports_remaining;
     api->second->incoming_imports.push_back(&unit_info);
 
@@ -1016,7 +1031,7 @@ static auto TrackImport(
     }
   } else {
     // The imported api is missing.
-    package_imports_it->second.has_load_error = true;
+    package_imports.has_load_error = true;
     CARBON_DIAGNOSTIC(LibraryApiNotFound, Error,
                       "Corresponding API for '{0}' not found.", std::string);
     CARBON_DIAGNOSTIC(ImportNotFound, Error, "Imported API '{0}' not found.",
@@ -1196,8 +1211,7 @@ auto CheckParseTrees(llvm::MutableArrayRef<Unit> units, bool prelude_import,
     // TODO: Better identify cycles, maybe try to untangle them.
     for (auto& unit_info : unit_infos) {
       if (unit_info.imports_remaining > 0) {
-        for (auto& [package_id, package_imports] :
-             unit_info.package_imports_map) {
+        for (auto& package_imports : unit_info.package_imports) {
           for (auto* import_it = package_imports.imports.begin();
                import_it != package_imports.imports.end();) {
             if (*import_it->unit_info->unit->sem_ir) {
diff --git a/toolchain/check/testdata/class/cross_package_import.carbon b/toolchain/check/testdata/class/cross_package_import.carbon
index 3689f8b42a98..ee1f7e1486d7 100644
--- a/toolchain/check/testdata/class/cross_package_import.carbon
+++ b/toolchain/check/testdata/class/cross_package_import.carbon
@@ -289,16 +289,16 @@ var c: Other.C = {};
 // CHECK:STDOUT:
 // CHECK:STDOUT: file {
 // CHECK:STDOUT:   package: <namespace> = namespace [template] {
-// CHECK:STDOUT:     .Other = %Other
 // CHECK:STDOUT:     .Core = %Core
+// CHECK:STDOUT:     .Other = %Other
 // CHECK:STDOUT:     .c = %c
 // CHECK:STDOUT:   }
-// CHECK:STDOUT:   %Other: <namespace> = namespace [template] {}
 // CHECK:STDOUT:   %Core: <namespace> = namespace [template] {}
+// CHECK:STDOUT:   %Other: <namespace> = namespace [template] {}
 // CHECK:STDOUT:   %Other.ref: <namespace> = name_ref Other, %Other [template = %Other]
-// CHECK:STDOUT:   %import_ref.1: type = import_ref ir1, inst+2, loaded [template = constants.%C]
-// CHECK:STDOUT:   %import_ref.2 = import_ref ir1, inst+3, unloaded
-// CHECK:STDOUT:   %import_ref.3 = import_ref ir2, inst+2, unloaded
+// CHECK:STDOUT:   %import_ref.1: type = import_ref ir2, inst+2, loaded [template = constants.%C]
+// CHECK:STDOUT:   %import_ref.2 = import_ref ir2, inst+3, unloaded
+// CHECK:STDOUT:   %import_ref.3 = import_ref ir3, inst+2, unloaded
 // CHECK:STDOUT:   %C.ref: type = name_ref C, %import_ref.1 [template = constants.%C]
 // CHECK:STDOUT:   %c.var: ref C = var c
 // CHECK:STDOUT:   %c: ref C = bind_name c, %c.var
diff --git a/toolchain/check/testdata/impl/lookup/import.carbon b/toolchain/check/testdata/impl/lookup/import.carbon
index 88bf801f1bb7..11a2dde98532 100644
--- a/toolchain/check/testdata/impl/lookup/import.carbon
+++ b/toolchain/check/testdata/impl/lookup/import.carbon
@@ -112,26 +112,26 @@ fn G(c: Impl.C) {
 // CHECK:STDOUT:
 // CHECK:STDOUT: file {
 // CHECK:STDOUT:   package: <namespace> = namespace [template] {
-// CHECK:STDOUT:     .Impl = %Impl
 // CHECK:STDOUT:     .Core = %Core
+// CHECK:STDOUT:     .Impl = %Impl
 // CHECK:STDOUT:     .G = %G.decl
 // CHECK:STDOUT:   }
-// CHECK:STDOUT:   %Impl: <namespace> = namespace [template] {}
 // CHECK:STDOUT:   %Core: <namespace> = namespace [template] {}
-// CHECK:STDOUT:   %import_ref.1 = import_ref ir1, inst+14, unloaded
-// CHECK:STDOUT:   %import_ref.2: <associated F in HasF> = import_ref ir1, inst+11, loaded [template = constants.%.6]
-// CHECK:STDOUT:   %import_ref.3 = import_ref ir1, inst+4, unloaded
-// CHECK:STDOUT:   %import_ref.4 = import_ref ir1, inst+6, unloaded
-// CHECK:STDOUT:   %import_ref.5: <witness> = import_ref ir1, inst+22, loaded [template = constants.%.7]
-// CHECK:STDOUT:   %import_ref.6: type = import_ref ir1, inst+13, loaded [template = constants.%C]
+// CHECK:STDOUT:   %Impl: <namespace> = namespace [template] {}
+// CHECK:STDOUT:   %import_ref.1 = import_ref ir2, inst+14, unloaded
+// CHECK:STDOUT:   %import_ref.2: <associated F in HasF> = import_ref ir2, inst+11, loaded [template = constants.%.6]
+// CHECK:STDOUT:   %import_ref.3 = import_ref ir2, inst+4, unloaded
+// CHECK:STDOUT:   %import_ref.4 = import_ref ir2, inst+6, unloaded
+// CHECK:STDOUT:   %import_ref.5: <witness> = import_ref ir2, inst+22, loaded [template = constants.%.7]
+// CHECK:STDOUT:   %import_ref.6: type = import_ref ir2, inst+13, loaded [template = constants.%C]
 // CHECK:STDOUT:   %G.decl: G = fn_decl @G [template = constants.%struct.1] {
 // CHECK:STDOUT:     %Impl.ref: <namespace> = name_ref Impl, %Impl [template = %Impl]
 // CHECK:STDOUT:     %C.ref: type = name_ref C, %import_ref.6 [template = constants.%C]
 // CHECK:STDOUT:     %c.loc4_6.1: C = param c
 // CHECK:STDOUT:     @G.%c: C = bind_name c, %c.loc4_6.1
 // CHECK:STDOUT:   }
-// CHECK:STDOUT:   %import_ref.7: type = import_ref ir1, inst+2, loaded [template = constants.%.2]
-// CHECK:STDOUT:   %import_ref.8 = import_ref ir1, inst+6, unloaded
+// CHECK:STDOUT:   %import_ref.7: type = import_ref ir2, inst+2, loaded [template = constants.%.2]
+// CHECK:STDOUT:   %import_ref.8 = import_ref ir2, inst+6, unloaded
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: interface @HasF {
diff --git a/toolchain/check/testdata/packages/cross_package_import.carbon b/toolchain/check/testdata/packages/cross_package_import.carbon
index f4b83bfaa801..37f62fa345b2 100644
--- a/toolchain/check/testdata/packages/cross_package_import.carbon
+++ b/toolchain/check/testdata/packages/cross_package_import.carbon
@@ -408,7 +408,7 @@ fn Other.G() {}
 // CHECK:STDOUT:   %import_ref.1: <namespace> = import_ref ir1, inst+2, loaded
 // CHECK:STDOUT:   %Other: <namespace> = namespace %import_ref.1, [template] {}
 // CHECK:STDOUT:   %Core: <namespace> = namespace [template] {}
-// CHECK:STDOUT:   %import_ref.2: F = import_ref ir2, inst+2, loaded [template = constants.%struct]
+// CHECK:STDOUT:   %import_ref.2: F = import_ref ir3, inst+2, loaded [template = constants.%struct]
 // CHECK:STDOUT:   %F.decl: F = fn_decl @F [template = constants.%struct] {}
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
diff --git a/toolchain/check/testdata/packages/explicit_imports.carbon b/toolchain/check/testdata/packages/explicit_imports.carbon
index 845bcff4efb7..75c326e65963 100644
--- a/toolchain/check/testdata/packages/explicit_imports.carbon
+++ b/toolchain/check/testdata/packages/explicit_imports.carbon
@@ -65,11 +65,11 @@ import library "lib";
 // CHECK:STDOUT:
 // CHECK:STDOUT: file {
 // CHECK:STDOUT:   package: <namespace> = namespace [template] {
-// CHECK:STDOUT:     .Api = %Api
 // CHECK:STDOUT:     .Core = %Core
+// CHECK:STDOUT:     .Api = %Api
 // CHECK:STDOUT:   }
-// CHECK:STDOUT:   %Api: <namespace> = namespace [template] {}
 // CHECK:STDOUT:   %Core: <namespace> = namespace [template] {}
+// CHECK:STDOUT:   %Api: <namespace> = namespace [template] {}
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: --- main_lib_api.carbon
diff --git a/toolchain/check/testdata/packages/fail_import_repeat.carbon b/toolchain/check/testdata/packages/fail_import_repeat.carbon
index a6d209ae7c1d..0d74cfd9997d 100644
--- a/toolchain/check/testdata/packages/fail_import_repeat.carbon
+++ b/toolchain/check/testdata/packages/fail_import_repeat.carbon
@@ -92,11 +92,11 @@ import library default;
 // CHECK:STDOUT:
 // CHECK:STDOUT: file {
 // CHECK:STDOUT:   package: <namespace> = namespace [template] {
-// CHECK:STDOUT:     .Api = %Api
 // CHECK:STDOUT:     .Core = %Core
+// CHECK:STDOUT:     .Api = %Api
 // CHECK:STDOUT:   }
-// CHECK:STDOUT:   %Api: <namespace> = namespace [template] {}
 // CHECK:STDOUT:   %Core: <namespace> = namespace [template] {}
+// CHECK:STDOUT:   %Api: <namespace> = namespace [template] {}
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: --- fail_default_import.carbon