diff --git a/clang/lib/Sema/SemaModule.cpp b/clang/lib/Sema/SemaModule.cpp
index 67c6556e00ddf..5ce5330b09466 100644
--- a/clang/lib/Sema/SemaModule.cpp
+++ b/clang/lib/Sema/SemaModule.cpp
@@ -636,11 +636,9 @@ void Sema::BuildModuleInclude(SourceLocation DirectiveLoc, Module *Mod) {
       TUKind == TU_Module &&
       getSourceManager().isWrittenInMainFile(DirectiveLoc);
 
-  bool ShouldAddImport = !IsInModuleIncludes;
-
-  // If this module import was due to an inclusion directive, create an
-  // implicit import declaration to capture it in the AST.
-  if (ShouldAddImport) {
+  // If we are really importing a module (not just checking layering) due to an
+  // #include in the main file, synthesize an ImportDecl.
+  if (getLangOpts().Modules && !IsInModuleIncludes) {
     TranslationUnitDecl *TU = getASTContext().getTranslationUnitDecl();
     ImportDecl *ImportD = ImportDecl::CreateImplicit(getASTContext(), TU,
                                                      DirectiveLoc, Mod,
diff --git a/clang/test/Modules/Inputs/modulemaps-nomodules/header.h b/clang/test/Modules/Inputs/modulemaps-nomodules/header.h
new file mode 100644
index 0000000000000..e69de29bb2d1d
diff --git a/clang/test/Modules/Inputs/modulemaps-nomodules/module.modulemap b/clang/test/Modules/Inputs/modulemaps-nomodules/module.modulemap
new file mode 100644
index 0000000000000..dcae7e5a37c3a
--- /dev/null
+++ b/clang/test/Modules/Inputs/modulemaps-nomodules/module.modulemap
@@ -0,0 +1,3 @@
+module M {
+  private header "header.h"
+}
diff --git a/clang/test/Modules/getSourceDescriptor-crash.cpp b/clang/test/Modules/getSourceDescriptor-crash.cpp
index 84e527aef91b5..53111786472f7 100644
--- a/clang/test/Modules/getSourceDescriptor-crash.cpp
+++ b/clang/test/Modules/getSourceDescriptor-crash.cpp
@@ -1,4 +1,5 @@
-// RUN: %clang_cc1 -I %S/Inputs/getSourceDescriptor-crash -S -emit-llvm -debug-info-kind=limited -debugger-tuning=lldb -fimplicit-module-maps %s -o - | FileCheck %s
+// RUN: rm -rf %t
+// RUN: %clang_cc1 -I %S/Inputs/getSourceDescriptor-crash -S -emit-llvm -debug-info-kind=limited -debugger-tuning=lldb -fmodules -fmodules-cache-path=%t -fimplicit-module-maps %s -o - | FileCheck %s
 
 #include "h1.h"
 #include "h1.h"
diff --git a/clang/test/Modules/modulemaps-nomodules.cpp b/clang/test/Modules/modulemaps-nomodules.cpp
new file mode 100644
index 0000000000000..eec024fa24b47
--- /dev/null
+++ b/clang/test/Modules/modulemaps-nomodules.cpp
@@ -0,0 +1,8 @@
+// Make sure we treat includes that are part of modulemaps the same as textual
+// headers when modules are not enabled (e.g do't generate import decls, but
+// still perform layering checks).
+// No need to pass -fno-modules explicitly, absence implies negation for cc1.
+// RUN: %clang_cc1 -I %S/Inputs/modulemaps-nomodules -fmodule-map-file=%S/Inputs/modulemaps-nomodules/module.modulemap %s -verify -ast-dump | FileCheck %s
+
+#include "header.h" // expected-error{{use of private header from outside its module: 'header.h'}}
+// CHECK-NOT: ImportDecl
diff --git a/clang/test/PCH/Inputs/modulemaps-nomodules/header.h b/clang/test/PCH/Inputs/modulemaps-nomodules/header.h
new file mode 100644
index 0000000000000..e69de29bb2d1d
diff --git a/clang/test/PCH/Inputs/modulemaps-nomodules/module.modulemap b/clang/test/PCH/Inputs/modulemaps-nomodules/module.modulemap
new file mode 100644
index 0000000000000..15b101f4be60e
--- /dev/null
+++ b/clang/test/PCH/Inputs/modulemaps-nomodules/module.modulemap
@@ -0,0 +1,3 @@
+module M {
+  header "header.h"
+}
diff --git a/clang/test/PCH/modulemaps-nomodules.cpp b/clang/test/PCH/modulemaps-nomodules.cpp
new file mode 100644
index 0000000000000..c18fabe4ac856
--- /dev/null
+++ b/clang/test/PCH/modulemaps-nomodules.cpp
@@ -0,0 +1,6 @@
+// Make sure we don't crash when serializing a PCH with an include from a
+// modulemap file in nomodules mode.
+// No need to pass -fno-modules explicitly, absence implies negation for cc1.
+// RUN: %clang_cc1 -I %S/Inputs/modulemaps-nomodules -fmodule-map-file=%S/Inputs/modulemaps-nomodules/module.modulemap %s -emit-pch -o /dev/null
+
+#include "header.h"