diff --git a/lib/Index/IndexRecord.cpp b/lib/Index/IndexRecord.cpp
index 8cc4d3997b8a0..d441ade35075f 100644
--- a/lib/Index/IndexRecord.cpp
+++ b/lib/Index/IndexRecord.cpp
@@ -416,14 +416,16 @@ static void addModuleDependencies(ArrayRef<ModuleDecl::ImportedModule> imports,
           StringRef moduleName = mod->getNameStr();
           bool withoutUnitName = true;
           if (FU->getKind() == FileUnitKind::ClangModule) {
-            withoutUnitName = false;
             auto clangModUnit = cast<ClangModuleUnit>(LFU);
-            if (auto clangMod = clangModUnit->getUnderlyingClangModule()) {
-              moduleName = clangMod->getTopLevelModuleName();
-              // FIXME: clang's -Rremarks do not seem to go through Swift's
-              // diagnostic emitter.
-              clang::index::emitIndexDataForModuleFile(clangMod,
-                                                       clangCI, unitWriter);
+            if (!clangModUnit->isSystemModule() || indexSystemModules) {
+              withoutUnitName = false;
+              if (auto clangMod = clangModUnit->getUnderlyingClangModule()) {
+                moduleName = clangMod->getTopLevelModuleName();
+                // FIXME: clang's -Rremarks do not seem to go through Swift's
+                // diagnostic emitter.
+                clang::index::emitIndexDataForModuleFile(clangMod,
+                                                         clangCI, unitWriter);
+              }
             }
           } else {
             // Serialized AST file.
diff --git a/test/Index/Store/ignore-system-clang-modules.swift b/test/Index/Store/ignore-system-clang-modules.swift
new file mode 100644
index 0000000000000..7147488165fdf
--- /dev/null
+++ b/test/Index/Store/ignore-system-clang-modules.swift
@@ -0,0 +1,35 @@
+// RUN: %empty-directory(%t)
+
+// Make a basic clang framework to import
+//
+// RUN: %empty-directory(%t/MySystemFramework.framework/Headers)
+// RUN: %empty-directory(%t/MySystemFramework.framework/Modules)
+// RUN: echo 'void someSystemFunc(int arg);' > %t/MySystemFramework.framework/Headers/MySystemFramework.h
+// RUN: echo 'framework module MySystemFramework { umbrella header "MySystemFramework.h" export * }' > %t/MySystemFramework.framework/Modules/module.modulemap
+
+import MySystemFramework
+someSystemFunc(2)
+
+// Index this file with and without ignoring system frameworks
+//
+// RUN: %target-swiftc_driver -index-store-path %t/idx1 -o %t/file.o -Fsystem %t -typecheck %s
+// RUN: %target-swiftc_driver -index-store-path %t/idx2 -o %t/file.o -index-ignore-system-modules -Fsystem %t -typecheck %s
+// RUN: c-index-test core -print-unit %t/idx1 | %FileCheck --check-prefixes=ALLOWSYSTEM,BOTH %s
+// RUN: c-index-test core -print-unit %t/idx2 | %FileCheck --check-prefixes=IGNORESYSTEM,BOTH %s
+
+// We should always get a dependency on the system framework in the unit for this file's module.
+//
+// BOTH: DEPEND START
+// BOTH: Unit | system | MySystemFramework |
+// BOTH: DEPEND END
+
+// We should get a unit for the system framework if not ignoring them.
+//
+// ALLOWSYSTEM: provider: clang
+// ALLOWSYSTEM-NEXT: is-system: 1
+// ALLOWSYSTEM-NEXT: is-module: 1
+// ALLOWSYSTEM-NEXT: module-name: MySystemFramework
+
+// But shouldn't if we are.
+//
+// IGNORESYSTEM-NOT: module-name: MySystemFramework