Index: lld/ELF/InputFiles.h
===================================================================
--- lld/ELF/InputFiles.h
+++ lld/ELF/InputFiles.h
@@ -381,12 +381,14 @@
 
   template <typename ELFT> void parse();
 
-  // Used for --no-allow-shlib-undefined.
-  bool allNeededIsKnown;
-
   // Used for --as-needed
   bool isNeeded;
 
+  // Non-weak undefined symbols which are not yet resolved when the SO is
+  // parsed. Only filled if we check unresolved symbols in shared libraries,
+  // i.e. (config->unresolvedSymbolsInShlib != UnresolvedPolicy::Ignore).
+  std::vector<Symbol *> requiredSymbols;
+
 private:
   template <typename ELFT>
   std::vector<uint32_t> parseVerneed(const llvm::object::ELFFile<ELFT> &obj,
Index: lld/ELF/InputFiles.cpp
===================================================================
--- lld/ELF/InputFiles.cpp
+++ lld/ELF/InputFiles.cpp
@@ -1567,6 +1567,9 @@
       Symbol *s = symtab->addSymbol(
           Undefined{this, name, sym.getBinding(), sym.st_other, sym.getType()});
       s->exportDynamic = true;
+      if (s->isUndefined() && !s->isWeak() &&
+          config->unresolvedSymbolsInShlib != UnresolvedPolicy::Ignore)
+        requiredSymbols.push_back(s);
       continue;
     }
 
Index: lld/ELF/Writer.cpp
===================================================================
--- lld/ELF/Writer.cpp
+++ lld/ELF/Writer.cpp
@@ -2006,6 +2006,10 @@
     in.iplt->addSymbols();
 
   if (config->unresolvedSymbolsInShlib != UnresolvedPolicy::Ignore) {
+    auto diagnose =
+        config->unresolvedSymbolsInShlib == UnresolvedPolicy::ReportError
+            ? errorOrWarn
+            : warn;
     // Error on undefined symbols in a shared object, if all of its DT_NEEDED
     // entries are seen. These cases would otherwise lead to runtime errors
     // reported by the dynamic linker.
@@ -2013,23 +2017,18 @@
     // ld.bfd traces all DT_NEEDED to emulate the logic of the dynamic linker to
     // catch more cases. That is too much for us. Our approach resembles the one
     // used in ld.gold, achieves a good balance to be useful but not too smart.
-    for (SharedFile *file : sharedFiles)
-      file->allNeededIsKnown =
+    for (SharedFile *file : sharedFiles) {
+      bool allNeededIsKnown =
           llvm::all_of(file->dtNeeded, [&](StringRef needed) {
             return symtab->soNames.count(needed);
           });
-
-    for (Symbol *sym : symtab->symbols())
-      if (sym->isUndefined() && !sym->isWeak())
-        if (auto *f = dyn_cast_or_null<SharedFile>(sym->file))
-          if (f->allNeededIsKnown) {
-            auto diagnose = config->unresolvedSymbolsInShlib ==
-                                    UnresolvedPolicy::ReportError
-                                ? errorOrWarn
-                                : warn;
-            diagnose(toString(f) + ": undefined reference to " +
-                     toString(*sym) + " [--no-allow-shlib-undefined]");
-          }
+      if (!allNeededIsKnown)
+        continue;
+      for (Symbol *sym : file->requiredSymbols)
+        if (sym->isUndefined() && !sym->isWeak())
+          diagnose(toString(file) + ": undefined reference to " +
+                   toString(*sym) + " [--no-allow-shlib-undefined]");
+    }
   }
 
   {
Index: lld/test/ELF/unresolved-in-dso.ll
===================================================================
--- /dev/null
+++ lld/test/ELF/unresolved-in-dso.ll
@@ -0,0 +1,15 @@
+# REQUIRES: x86
+
+# RUN: echo 'callq undef@PLT' | \
+# RUN:   llvm-mc -filetype=obj -triple=x86_64 - -o %ta.o
+# RUN: echo '.globl _shared; _shared: callq undef@PLT' | \
+# RUN:   llvm-mc -filetype=obj -triple=x86_64 - -o %tb.o
+# RUN: ld.lld %tb.o -o %tb.so -shared
+# RUN: llvm-mc -filetype=obj -triple=x86_64 %s -o %t.o
+# RUN: not ld.lld --gc-sections %t.o %ta.o %tb.so -o /dev/null 2>&1 | \
+# RUN:   FileCheck %s
+
+# CHECK: error: {{.*}}.so: undefined reference to undef [--no-allow-shlib-undefined]
+
+.globl _start
+_start: