diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index 143fbc7feb3ab..29b81c1a753cf 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -2630,6 +2630,14 @@ InputFile ASTReader::getInputFile(ModuleFile &F, unsigned ID, bool Complain) {
       F.StandardCXXModule && FileChange.Kind == Change::None)
     FileChange = HasInputContentChanged(FileChange);
 
+  // When we have StoredTime equal to zero and ValidateASTInputFilesContent,
+  // it is better to check the content of the input files because we cannot rely
+  // on the file modification time, which will be the same (zero) for these
+  // files.
+  if (!StoredTime && ValidateASTInputFilesContent &&
+      FileChange.Kind == Change::None)
+    FileChange = HasInputContentChanged(FileChange);
+
   // For an overridden file, there is nothing to validate.
   if (!Overridden && FileChange.Kind != Change::None) {
     if (Complain && !Diags.isDiagnosticInFlight()) {
diff --git a/clang/test/Modules/implicit-module-no-timestamp.cpp b/clang/test/Modules/implicit-module-no-timestamp.cpp
new file mode 100644
index 0000000000000..1b681a610bab2
--- /dev/null
+++ b/clang/test/Modules/implicit-module-no-timestamp.cpp
@@ -0,0 +1,34 @@
+// UNSUPPORTED: system-windows
+// RUN: rm -rf %t
+// RUN: split-file %s %t
+// RUN: cd %t
+//
+// RUN: cp a1.h a.h
+// RUN: %clang_cc1 -fmodules -fvalidate-ast-input-files-content -fno-pch-timestamp -fmodule-map-file=module.modulemap -fmodules-cache-path=%t test1.cpp
+// RUN: cp a2.h a.h
+// RUN: %clang_cc1 -fmodules -fvalidate-ast-input-files-content -fno-pch-timestamp -fmodule-map-file=module.modulemap -fmodules-cache-path=%t test2.cpp
+
+//--- a1.h
+#define FOO
+
+//--- a2.h
+#define BAR
+
+//--- module.modulemap
+module a {
+  header "a.h"
+}
+
+//--- test1.cpp
+#include "a.h"
+
+#ifndef FOO
+#error foo
+#endif
+
+//--- test2.cpp
+#include "a.h"
+
+#ifndef BAR
+#error bar
+#endif