Index: lib/Core/SymbolTable.cpp
===================================================================
--- lib/Core/SymbolTable.cpp
+++ lib/Core/SymbolTable.cpp
@@ -339,6 +339,12 @@
     return false;
   if (l->size() != r->size())
     return false;
+  if (l->sectionChoice() != r->sectionChoice())
+    return false;
+  if (l->sectionChoice() == DefinedAtom::sectionCustomRequired) {
+    if (!l->customSectionName().equals(r->customSectionName()))
+      return false;
+  }
   ArrayRef<uint8_t> lc = l->rawContent();
   ArrayRef<uint8_t> rc = r->rawContent();
   return memcmp(lc.data(), rc.data(), lc.size()) == 0;
Index: test/core/custom-section-coalesce.objtxt
===================================================================
--- /dev/null
+++ test/core/custom-section-coalesce.objtxt
@@ -0,0 +1,78 @@
+# RUN: lld -core %s | FileCheck %s
+
+#
+# Test that custom sections are preserved when duplicate merge-by-content
+# constants are coalesced.
+#
+
+---
+defined-atoms:
+    - ref-name:          L1
+      type:              constant
+      merge:             by-content
+      content:           [ 01, 02, 03, 04 ]
+      section-choice:    custom-required
+      section-name:      .mysection
+
+    - ref-name:          L2
+      type:              constant
+      merge:             by-content
+      content:           [ 05, 06, 07, 08 ]
+      section-choice:    custom-required
+      section-name:      .mysection
+
+    - ref-name:          L3
+      type:              constant
+      merge:             by-content
+      content:           [ 01, 02, 03, 04 ]
+
+---
+defined-atoms:
+    - ref-name:          L1
+      type:              constant
+      merge:             by-content
+      content:           [ 01, 02, 03, 04 ]
+      section-choice:    custom-required
+      section-name:      .mysection
+
+    - ref-name:          L2
+      type:              constant
+      merge:             by-content
+      content:           [ 01, 02, 03, 04 ]
+      section-choice:    custom-required
+      section-name:      .mysection2
+---
+defined-atoms:
+    - ref-name:          L1
+      type:              constant
+      merge:             by-content
+      content:           [ 05, 06, 07, 08 ]
+      section-choice:    custom-required
+      section-name:      .mysection
+
+    - ref-name:          L2
+      type:              constant
+      merge:             by-content
+      content:           [ 01, 02, 03, 04 ]
+...
+
+
+# CHECK:defined-atoms:
+# CHECK:  - type:            constant
+# CHECK:    content:         [ 01, 02, 03, 04 ]
+# CHECK:    merge:           by-content
+# CHECK:    section-choice:  custom-required
+# CHECK:    section-name:    .mysection
+# CHECK:  - type:            constant
+# CHECK:    content:         [ 05, 06, 07, 08 ]
+# CHECK:    merge:           by-content
+# CHECK:    section-choice:  custom-required
+# CHECK:    section-name:    .mysection
+# CHECK:  - type:            constant
+# CHECK:    content:         [ 01, 02, 03, 04 ]
+# CHECK:    merge:           by-content
+# CHECK:  - type:            constant
+# CHECK:    content:         [ 01, 02, 03, 04 ]
+# CHECK:    merge:           by-content
+# CHECK:    section-choice:  custom-required
+# CHECK:    section-name:    .mysection2