diff --git a/include/swift/AST/ModuleDependencies.h b/include/swift/AST/ModuleDependencies.h
index f6a057a45ed..7d3d27ae803 100644
--- a/include/swift/AST/ModuleDependencies.h
+++ b/include/swift/AST/ModuleDependencies.h
@@ -724,7 +724,7 @@ public:
       // Special case: a submodule named "Foo.Private" can be moved to a top-level
       // module named "Foo_Private". ClangImporter has special support for this.
       if (submoduleComponent.Item.str() == "Private")
-        ImportedModuleName = ImportedModuleName + "_Private";
+        addOptionalModuleImport(ImportedModuleName + "_Private", alreadyAddedModules);
     }
 
     addModuleImport(ImportedModuleName, alreadyAddedModules);
diff --git a/test/ScanDependencies/Inputs/CHeaders/Y.h b/test/ScanDependencies/Inputs/CHeaders/Y.h
new file mode 100644
index 00000000000..e385076888c
--- /dev/null
+++ b/test/ScanDependencies/Inputs/CHeaders/Y.h
@@ -0,0 +1 @@
+void funcY(void);
diff --git a/test/ScanDependencies/Inputs/CHeaders/Y_Private.h b/test/ScanDependencies/Inputs/CHeaders/Y_Private.h
new file mode 100644
index 00000000000..b6991bc8939
--- /dev/null
+++ b/test/ScanDependencies/Inputs/CHeaders/Y_Private.h
@@ -0,0 +1 @@
+void funcYPrivate(void);
diff --git a/test/ScanDependencies/Inputs/CHeaders/module.modulemap b/test/ScanDependencies/Inputs/CHeaders/module.modulemap
index d37a3148d0c..2957143d73c 100644
--- a/test/ScanDependencies/Inputs/CHeaders/module.modulemap
+++ b/test/ScanDependencies/Inputs/CHeaders/module.modulemap
@@ -46,3 +46,10 @@ module X_Private {
   header "X_Private.h"
   export *
 }
+module Y {
+  header "Y.h"
+  export *
+  explicit module Private {
+    header "Y_Private.h"
+  }
+}
\ No newline at end of file
diff --git a/test/ScanDependencies/module_deps_clang_private_submodule.swift b/test/ScanDependencies/module_deps_clang_private_submodule.swift
index 02dbcd163f1..c12c77dbeda 100644
--- a/test/ScanDependencies/module_deps_clang_private_submodule.swift
+++ b/test/ScanDependencies/module_deps_clang_private_submodule.swift
@@ -1,7 +1,9 @@
 // RUN: %empty-directory(%t.module-cache)
-// RUN: %target-swift-frontend -scan-dependencies -module-cache-path %t.module-cache %s -o %t.deps.json -I %S/Inputs/CHeaders
+// RUN: %target-swift-frontend -scan-dependencies -module-cache-path %t.module-cache %s -o %t.deps.json -I %S/Inputs/CHeaders -verify
 
 // RUN: %validate-json %t.deps.json | %FileCheck %s
 // CHECK: "clang": "X_Private"
+// CHECK: "clang": "Y"
+// CHECK-NOT: "clang": "Y_Private"
 import X.Private
-
+import Y.Private