diff --git a/llvm/lib/Transforms/IPO/FunctionImport.cpp b/llvm/lib/Transforms/IPO/FunctionImport.cpp
--- a/llvm/lib/Transforms/IPO/FunctionImport.cpp
+++ b/llvm/lib/Transforms/IPO/FunctionImport.cpp
@@ -1349,9 +1349,16 @@
       }
     }
 
+    // Skip upgrading debug info if the producer versions of both modules match.
+    bool ShouldUpgradeDebugInfo = true;
+    if (NamedMDNode *SrcMD = SrcModule->getNamedMetadata("llvm.ident"))
+      if (NamedMDNode *DestMD = DestModule.getNamedMetadata("llvm.ident"))
+        ShouldUpgradeDebugInfo = SrcMD->getName() != DestMD->getName();
+
     // Upgrade debug info after we're done materializing all the globals and we
     // have loaded all the required metadata!
-    UpgradeDebugInfo(*SrcModule);
+    if (ShouldUpgradeDebugInfo)
+      UpgradeDebugInfo(*SrcModule);
 
     // Set the partial sample profile ratio in the profile summary module flag
     // of the imported source module, if applicable, so that the profile summary
diff --git a/llvm/test/LTO/X86/Inputs/strip-debug-info-bar-ident.ll b/llvm/test/LTO/X86/Inputs/strip-debug-info-bar-ident.ll
new file mode 100644
--- /dev/null
+++ b/llvm/test/LTO/X86/Inputs/strip-debug-info-bar-ident.ll
@@ -0,0 +1,16 @@
+target datalayout = "e-m:o-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.12"
+
+define void @bar() !dbg !3 {
+  ret void
+}
+
+!llvm.module.flags = !{!0}
+!llvm.dbg.cu = !{!1}
+!llvm.ident = !{!4}
+
+!0 = !{i32 2, !"Debug Info Version", i32 3}
+!1 = distinct !DICompileUnit(language: DW_LANG_C99, file: !2)
+!2 = !DIFile(filename: "broken", directory: "")
+!3 = distinct !DISubprogram(line: 1000, isDefinition: true)
+!4 = !{!"version 42"}
diff --git a/llvm/test/LTO/X86/strip-debug-info.ll b/llvm/test/LTO/X86/strip-debug-info.ll
--- a/llvm/test/LTO/X86/strip-debug-info.ll
+++ b/llvm/test/LTO/X86/strip-debug-info.ll
@@ -13,6 +13,8 @@
 ; RUN: opt -disable-verify -disable-upgrade-debug-info -module-summary %s -o %t.bc
 ; RUN: opt -disable-verify -disable-upgrade-debug-info -module-summary %S/Inputs/strip-debug-info-bar.ll \
 ; RUN:     -o %t2.bc
+; RUN: opt -disable-verify -disable-upgrade-debug-info -module-summary %S/Inputs/strip-debug-info-bar-ident.ll \
+; RUN:     -o %t3.bc
 ; RUN: llvm-lto -thinlto -thinlto-action=run \
 ; RUN:     %t.bc -disable-verify 2>&1 | \
 ; RUN:     FileCheck %s -allow-empty -check-prefix=CHECK-WARN
@@ -24,10 +26,18 @@
 ; RUN:     -exported-symbol foo -exported-symbol _foo \
 ; RUN:     %t-stripped.bc -disable-verify 2>&1 | \
 ; RUN:     FileCheck %s -allow-empty -check-prefix=CHECK-WARN
+; ---- Thin LTO (optimize, don't strip imported file due to matching llvm.ident)
+; RUN: llvm-lto -thinlto-action=thinlink -o %t.index.bc %t-stripped.bc %t3.bc
+; RUN: llvm-lto -thinlto -thinlto-action=import \
+; RUN:     -thinlto-index=%t.index.bc \
+; RUN:     -exported-symbol foo -exported-symbol _foo \
+; RUN:     %t-stripped.bc -disable-verify 2>&1 | \
+; RUN:     FileCheck %s -allow-empty -check-prefix=CHECK-NO-WARN
 
 ; CHECK-WARN: warning{{.*}} ignoring invalid debug info
 ; CHECK-WARN-NOT: Broken module found
 ; CHECK: foo
+; CHECK-NO-WARN-NOT: ignoring invalid debug info
 target datalayout = "e-m:o-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-apple-macosx10.12"
 
@@ -40,6 +50,8 @@
 
 !llvm.module.flags = !{!0}
 !llvm.dbg.cu = !{!1}
+!llvm.ident = !{!2}
 
 !0 = !{i32 2, !"Debug Info Version", i32 3}
 !1 = !DIFile(filename: "broken", directory: "")
+!2 = !{!"version 42"}