diff --git a/toolchain/lower/file_context.cpp b/toolchain/lower/file_context.cpp
index 05d3f257ada3..79e87d8d642f 100644
--- a/toolchain/lower/file_context.cpp
+++ b/toolchain/lower/file_context.cpp
@@ -139,12 +139,45 @@ auto FileContext::LowerDefinitions() -> void {
   // variables.
   if (auto global_ctor_id = sem_ir().global_ctor_id();
       global_ctor_id.has_value()) {
-    auto llvm_function = BuildFunctionDecl(global_ctor_id);
-    functions_.Set(global_ctor_id, llvm_function);
+    // This is basically an inlined and specialized version of
+    // `BuildFunctionDecl` because global_ctor is a bit special (it has no
+    // declarations, for one thing).
+    // TODO: Consider making the global ctor not a function at all, but a
+    // special block.
+    auto function_type_info = BuildFunctionTypeInfo(
+        {{this, global_ctor_id, SemIR::SpecificId::None}});
+    std::string mangled_name = "_C__global_init.";
+    auto package_id = sem_ir().package_id();
+    if (auto ident_id = package_id.AsIdentifierId(); ident_id.has_value()) {
+      mangled_name += sem_ir().identifiers().Get(ident_id);
+    } else {
+      mangled_name += package_id.AsSpecialName();
+    }
+
+    auto* llvm_function = llvm_module().getFunction(mangled_name);
+
+    if (!llvm_function) {
+      llvm_function = llvm::Function::Create(function_type_info.type,
+                                             llvm::Function::InternalLinkage,
+                                             mangled_name, llvm_module());
+      CARBON_CHECK(llvm_function->getName() == mangled_name,
+                   "Mangled name collision: {0}", mangled_name);
+    }
+    FunctionInfo function_info = {
+        .type = function_type_info.type,
+        .di_type = function_type_info.di_type,
+        .lowered_param_indices =
+            std::move(function_type_info.lowered_param_indices),
+        .unused_param_indices =
+            std::move(function_type_info.unused_param_indices),
+        .llvm_function = llvm_function,
+        .inexact = function_type_info.inexact};
+    functions_.Set(global_ctor_id, function_info);
+
     const auto& global_ctor = sem_ir().functions().Get(global_ctor_id);
     BuildFunctionBody(global_ctor_id, SemIR::SpecificId::None, global_ctor,
                       *this, global_ctor);
-    llvm::appendToGlobalCtors(llvm_module(), llvm_function->llvm_function,
+    llvm::appendToGlobalCtors(llvm_module(), llvm_function,
                               /*Priority=*/0);
   }
 }
diff --git a/toolchain/lower/testdata/var/global.carbon b/toolchain/lower/testdata/var/global.carbon
index 356dfb07d627..3c36308ac534 100644
--- a/toolchain/lower/testdata/var/global.carbon
+++ b/toolchain/lower/testdata/var/global.carbon
@@ -44,6 +44,12 @@ library "[[@TEST_NAME]]";
 var (_: i32, x: i32) = (1, 2);
 var (_: i32, _: i32) = (3, 4);
 
+// --- not_main_package.carbon
+
+package Other;
+
+var a: i32 = 1;
+
 // CHECK:STDOUT: ; ModuleID = 'simple.carbon'
 // CHECK:STDOUT: source_filename = "simple.carbon"
 // CHECK:STDOUT:
@@ -224,3 +230,30 @@ var (_: i32, _: i32) = (3, 4);
 // CHECK:STDOUT: !7 = !DILocation(line: 4, column: 1, scope: !4)
 // CHECK:STDOUT: !8 = !DILocation(line: 5, column: 1, scope: !4)
 // CHECK:STDOUT: !9 = !DILocation(line: 0, scope: !4)
+// CHECK:STDOUT: ; ModuleID = 'not_main_package.carbon'
+// CHECK:STDOUT: source_filename = "not_main_package.carbon"
+// CHECK:STDOUT:
+// CHECK:STDOUT: @_Ca.Other = global i32 0
+// CHECK:STDOUT: @llvm.global_ctors = appending global [1 x { i32, ptr, ptr }] [{ i32, ptr, ptr } { i32 0, ptr @_C__global_init.Other, ptr null }]
+// CHECK:STDOUT:
+// CHECK:STDOUT: ; Function Attrs: nounwind
+// CHECK:STDOUT: define internal void @_C__global_init.Other() #0 !dbg !4 {
+// CHECK:STDOUT: entry:
+// CHECK:STDOUT:   store i32 1, ptr @_Ca.Other, align 4, !dbg !7
+// CHECK:STDOUT:   ret void, !dbg !8
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: attributes #0 = { nounwind }
+// CHECK:STDOUT:
+// CHECK:STDOUT: !llvm.module.flags = !{!0, !1}
+// CHECK:STDOUT: !llvm.dbg.cu = !{!2}
+// CHECK:STDOUT:
+// CHECK:STDOUT: !0 = !{i32 7, !"Dwarf Version", i32 5}
+// CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
+// CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
+// CHECK:STDOUT: !3 = !DIFile(filename: "not_main_package.carbon", directory: "")
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "__global_init", linkageName: "_C__global_init.Other", scope: null, file: !3, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
+// CHECK:STDOUT: !6 = !{null}
+// CHECK:STDOUT: !7 = !DILocation(line: 4, column: 1, scope: !4)
+// CHECK:STDOUT: !8 = !DILocation(line: 0, scope: !4)