diff --git a/clang/lib/Basic/SourceLocation.cpp b/clang/lib/Basic/SourceLocation.cpp
--- a/clang/lib/Basic/SourceLocation.cpp
+++ b/clang/lib/Basic/SourceLocation.cpp
@@ -199,6 +199,10 @@
 
   std::pair<SourceLocation, StringRef> ImportLoc =
       SrcMgr->getModuleImportLoc(*this);
+
+  if (!ImportLoc.first.isValid())
+    return std::make_pair(FullSourceLoc(), ImportLoc.second);
+
   return std::make_pair(FullSourceLoc(ImportLoc.first, *SrcMgr),
                         ImportLoc.second);
 }
diff --git a/clang/test/Modules/Inputs/explicit-build-diags/a.h b/clang/test/Modules/Inputs/explicit-build-diags/a.h
new file mode 100644
--- /dev/null
+++ b/clang/test/Modules/Inputs/explicit-build-diags/a.h
@@ -0,0 +1 @@
+void a() __attribute__((deprecated));
diff --git a/clang/test/Modules/Inputs/explicit-build-diags/module.modulemap b/clang/test/Modules/Inputs/explicit-build-diags/module.modulemap
new file mode 100644
--- /dev/null
+++ b/clang/test/Modules/Inputs/explicit-build-diags/module.modulemap
@@ -0,0 +1 @@
+module a { header "a.h" }
diff --git a/clang/test/Modules/explicit-build-diags.cpp b/clang/test/Modules/explicit-build-diags.cpp
new file mode 100644
--- /dev/null
+++ b/clang/test/Modules/explicit-build-diags.cpp
@@ -0,0 +1,8 @@
+// RUN: rm -rf %t && mkdir %t
+// RUN: %clang_cc1 -fmodules -x c++ %S/Inputs/explicit-build-diags/module.modulemap -fmodule-name=a -emit-module -o %t/a.pcm
+// RUN: %clang_cc1 -fmodules -Wdeprecated-declarations -fdiagnostics-show-note-include-stack -serialize-diagnostic-file %t/tu.dia \
+// RUN:   -I %S/Inputs/explicit-build-diags -fmodule-file=%t/a.pcm -fsyntax-only %s
+
+#include "a.h"
+
+void foo() { a(); }