diff --git a/lld/MachO/InputFiles.cpp b/lld/MachO/InputFiles.cpp
--- a/lld/MachO/InputFiles.cpp
+++ b/lld/MachO/InputFiles.cpp
@@ -925,6 +925,12 @@
       }
       uint64_t add = r.addend;
       if (auto *sym = cast_or_null<Defined>(r.referent.dyn_cast<Symbol *>())) {
+        // Check whether the symbol defined in this file is the prevailing one.
+        // Skip if it is e.g. a weak def that didn't prevail.
+        if (sym->getFile() != this) {
+          ++it;
+          continue;
+        }
         add += sym->value;
         referentIsec = cast<ConcatInputSection>(sym->isec);
       } else {
diff --git a/lld/test/MachO/weak-definition-gc.s b/lld/test/MachO/weak-definition-gc.s
--- a/lld/test/MachO/weak-definition-gc.s
+++ b/lld/test/MachO/weak-definition-gc.s
@@ -30,19 +30,29 @@
 ## Test that omitted weak symbols don't add entries to the compact unwind table.
 # RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin19.0.0 %t/weak-sub-lsda.s -o %t/weak-sub-lsda.o
 # RUN: %lld -dylib -lc++ -o %t/out.dylib %t/weak-sub-lsda.o %t/weak-sub-lsda.o
-# RUN: llvm-objdump --macho --unwind-info --syms %t/out.dylib | FileCheck %s --check-prefix=UNWIND -D#%x,BASE=0
-
-# UNWIND:      SYMBOL TABLE:
-# UNWIND-DAG:  [[#%x,FOO:]]       w  F __TEXT,__text _foo
-# UNWIND-NOT:                          __TEXT,__text _foo
-
-# UNWIND:      Contents of __unwind_info section:
-# UNWIND:        LSDA descriptors:
-# UNWIND:           [0]: function offset=0x[[#%.8x,FOO-BASE]]
-# UNWIND-NOT:       [1]:
-# UNWIND:        Second level indices:
-# UNWIND-DAG:      [0]: function offset=0x[[#%.8x,FOO-BASE]]
-# UNWIND-NOT:      [1]:
+# RUN: llvm-objdump --macho --unwind-info --syms %t/out.dylib | FileCheck %s --check-prefix=ONE-UNWIND
+# RUN: %lld -dylib -lc++ -o %t/out.dylib %t/weak-sub.o %t/weak-sub-lsda.o
+# RUN: llvm-objdump --macho --unwind-info --syms %t/out.dylib | FileCheck %s --check-prefix=NO-UNWIND
+# RUN: yaml2obj %t/weak-sub-lsda-r.yaml > %t/weak-sub-lsda-r.o
+# RUN: %lld -dylib -lc++ -o %t/out.dylib %t/weak-sub.o %t/weak-sub-lsda-r.o
+# RUN: llvm-objdump --macho --unwind-info --syms %t/out.dylib | FileCheck %s --check-prefix=NO-UNWIND
+
+# ONE-UNWIND:      SYMBOL TABLE:
+# ONE-UNWIND-DAG:  [[#%x,FOO:]]       w  F __TEXT,__text _foo
+# ONE-UNWIND-NOT:                          __TEXT,__text _foo
+
+# ONE-UNWIND:      Contents of __unwind_info section:
+# ONE-UNWIND:        LSDA descriptors:
+# ONE-UNWIND:           [0]: function offset=0x[[#%.8x,FOO]]
+# ONE-UNWIND-NOT:       [1]:
+# ONE-UNWIND:        Second level indices:
+# ONE-UNWIND-DAG:      [0]: function offset=0x[[#%.8x,FOO]]
+# ONE-UNWIND-NOT:      [1]:
+
+# NO-UNWIND:      SYMBOL TABLE:
+# NO-UNWIND-DAG:  [[#%x,FOO:]]       w  F __TEXT,__text _foo
+# NO-UNWIND-NOT:                          __TEXT,__text _foo
+# NO-UNWIND-NOT:  Contents of __unwind_info section:
 
 ## Test interaction with .alt_entry
 ## FIXME: ld64 manages to strip both one copy of _foo and _bar each.
@@ -246,3 +256,227 @@
   retq
 
 .subsections_via_symbols
+
+#--- weak-sub-lsda-r.yaml
+## This was generated from compiling weak-sub-lsda.s above at rev a2404f11c77e
+## and then running it through `ld -r`. This converts a number of unwind-related
+## relocations from section- to symbol-based ones.
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