Index: lib/AST/ASTImporter.cpp
===================================================================
--- lib/AST/ASTImporter.cpp
+++ lib/AST/ASTImporter.cpp
@@ -1221,6 +1221,10 @@
     // If the field looks like this:
     // struct { ... } A;
     QualType FieldType = F->getType();
+    // In case of nested structs.
+    while (const auto *ElabType = dyn_cast<ElaboratedType>(FieldType)) {
+      FieldType = ElabType->getNamedType();
+    }
     if (const auto *RecType = dyn_cast<RecordType>(FieldType)) {
       const RecordDecl *RecDecl = RecType->getDecl();
       if (RecDecl->getDeclContext() == Owner &&
@@ -3030,9 +3034,8 @@
       }
       
       if (RecordDecl *FoundRecord = dyn_cast<RecordDecl>(Found)) {
-        if (D->isAnonymousStructOrUnion() && 
-            FoundRecord->isAnonymousStructOrUnion()) {
-          // If both anonymous structs/unions are in a record context, make sure
+        if (!SearchName) {
+          // If both unnamed structs/unions are in a record context, make sure
           // they occur in the same location in the context records.
           if (Optional<unsigned> Index1
               = findUntaggedStructOrUnionIndex(D)) {
@@ -3076,8 +3079,6 @@
               
           AdoptDecl = FoundRecord;
           continue;
-        } else if (!SearchName) {
-          continue;
         }
       }
       
Index: test/ASTMerge/struct/Inputs/struct1.c
===================================================================
--- test/ASTMerge/struct/Inputs/struct1.c
+++ test/ASTMerge/struct/Inputs/struct1.c
@@ -61,3 +61,65 @@
   Int i;
   float f;
 } x11;
+
+//Matches
+struct Unnamed {
+  union {
+    struct {
+      int i;
+    } S;
+    struct {
+      float i;
+    } R;
+  } U;
+} x12;
+
+//Matches
+struct DeepUnnamed {
+  union {
+    union {
+      struct {
+        long i;
+      } S;
+      struct {
+        int i;
+      } R;
+    } U1;
+    union {
+      struct {
+        long i;
+      } S;
+      struct {
+        float i;
+      } T;
+    } U2;
+  } U;
+  struct {
+    long i;
+  } V;
+} x13;
+
+// Mismatch due to unnamed struct used internally
+struct DeepUnnamedError {
+  union {
+    union {
+      struct {
+        long i;
+      } S;
+      struct {
+        int i;
+      } R;
+    } U1;
+    union {
+      struct {
+        long i;
+      } S;
+      struct {
+        float i;
+      } T;
+    } U2;
+  } U;
+  struct {
+    long i;
+  } V;
+} x14;
\ No newline at end of file
Index: test/ASTMerge/struct/Inputs/struct2.c
===================================================================
--- test/ASTMerge/struct/Inputs/struct2.c
+++ test/ASTMerge/struct/Inputs/struct2.c
@@ -58,3 +58,65 @@
   int i;
   float f;
 } x11;
+
+//Matches
+struct Unnamed {
+  union {
+    struct {
+      int i;
+    } S;
+    struct {
+      float i;
+    } R;
+  } U;
+} x12;
+
+//Matches
+struct DeepUnnamed {
+  union {
+    union {
+      struct {
+        long i;
+      } S;
+      struct {
+        int i;
+      } R;
+    } U1;
+    union {
+      struct {
+        long i;
+      } S;
+      struct {
+        float i;
+      } T;
+    } U2;
+  } U;
+  struct {
+    long i;
+  } V;
+} x13;
+
+// Mismatch due to unnamed struct used internally
+struct DeepUnnamedError {
+  union {
+    union {
+      struct {
+        long i;
+      } S;
+      struct {
+        int i;
+      } R;
+    } U1;
+    union {
+      struct {
+        float i;
+      } S;
+      struct {
+        float i;
+      } T;
+    } U2;
+  } U;
+  struct {
+    long i;
+  } V;
+} x14;
Index: test/ASTMerge/struct/test.c
===================================================================
--- test/ASTMerge/struct/test.c
+++ test/ASTMerge/struct/test.c
@@ -39,4 +39,12 @@
 // CHECK: struct2.c:53:43: note: field 'Deeper' has type 'struct DeeperError *' here
 // CHECK: struct2.c:54:3: error: external variable 'xDeep' declared with incompatible types in different translation units ('struct DeepError' vs. 'struct DeepError')
 // CHECK: struct1.c:57:3: note: declared here with type 'struct DeepError'
-// CHECK: 8 warnings and 7 errors generated
+// CHECK: struct1.c:114:7: warning: type 'struct DeepUnnamedError::(anonymous at [[PATH_TO_INPUTS:.+]]/struct1.c:114:7)' has incompatible definitions in different translation units
+// CHECK: struct1.c:115:14: note: field 'i' has type 'long' here
+// CHECK: struct2.c:112:15: note: field 'i' has type 'float' here
+// CHECK: struct1.c:113:5: warning: type 'union DeepUnnamedError::(anonymous at [[PATH_TO_INPUTS]]/struct1.c:113:5)' has incompatible definitions in different translation units
+// CHECK: struct1.c:116:9: note: field 'S' has type 'struct (anonymous struct at [[PATH_TO_INPUTS]]/struct1.c:114:7)' here
+// CHECK: struct2.c:113:9: note: field 'S' has type 'struct (anonymous struct at [[PATH_TO_INPUTS]]/struct2.c:111:7)' here
+// CHECK: struct2.c:122:3: error: external variable 'x14' declared with incompatible types in different translation units ('struct DeepUnnamedError' vs. 'struct DeepUnnamedError')
+// check: struct1.c:125:3: note: declared here with type 'struct DeepUnnamedError'
+// CHECK: 10 warnings and 8 errors generated