diff --git a/lib/MC/ELFObjectWriter.cpp b/lib/MC/ELFObjectWriter.cpp
index 5b8b013ad08..89f3b30cddd 100644
--- a/lib/MC/ELFObjectWriter.cpp
+++ b/lib/MC/ELFObjectWriter.cpp
@@ -669,6 +669,20 @@ void ELFWriter::computeSymbolTable(
     } else {
       const MCSectionELF &Section =
           static_cast<const MCSectionELF &>(Symbol.getSection());
+
+      // We may end up with a situation when section symbol is technically
+      // defined, but should not be. That happens because we explicitly
+      // pre-create few .debug_* sections to have accessors.
+      // And if these sections were not really defined in the code, but were
+      // referenced, we simply error out.
+      if (!Section.isRegistered()) {
+        assert(static_cast<const MCSymbolELF &>(Symbol).getType() ==
+               ELF::STT_SECTION);
+        Ctx.reportError(SMLoc(),
+                        "Undefined section reference: " + Symbol.getName());
+        continue;
+      }
+
       if (Mode == NonDwoOnly && isDwoSection(Section))
         continue;
       MSD.SectionIndex = SectionIndexMap.lookup(&Section);
diff --git a/lib/MC/MCFragment.cpp b/lib/MC/MCFragment.cpp
index 0ebcf21a422..f2e08184c72 100644
--- a/lib/MC/MCFragment.cpp
+++ b/lib/MC/MCFragment.cpp
@@ -238,7 +238,7 @@ MCFragment::~MCFragment() = default;
 MCFragment::MCFragment(FragmentType Kind, bool HasInstructions,
                        MCSection *Parent)
     : Kind(Kind), HasInstructions(HasInstructions), Parent(Parent),
-      Atom(nullptr), Offset(~UINT64_C(0)) {
+      Atom(nullptr), Offset(~UINT64_C(0)), LayoutOrder(0) {
   if (Parent && !isDummy())
     Parent->getFragmentList().push_back(this);
 }
diff --git a/test/MC/ELF/undefined-debug.s b/test/MC/ELF/undefined-debug.s
new file mode 100644
index 00000000000..95ead70ef97
--- /dev/null
+++ b/test/MC/ELF/undefined-debug.s
@@ -0,0 +1,5 @@
+// RUN: not llvm-mc -filetype=obj -triple x86_64-pc-linux-gnu %s -o %t 2>&1 | FileCheck %s
+// CHECK: error: Undefined section reference: .debug_pubnames
+
+.section .foo,"",@progbits
+  .long  .debug_pubnames