Index: lld/COFF/SymbolTable.cpp
===================================================================
--- lld/COFF/SymbolTable.cpp
+++ lld/COFF/SymbolTable.cpp
@@ -34,6 +34,21 @@
   return s;
 }
 
+static bool compatibleMachineType(COFFLinkerContext &ctx, MachineTypes mt) {
+  if (mt == IMAGE_FILE_MACHINE_UNKNOWN)
+    return true;
+  switch (ctx.config.machine) {
+  case ARM64:
+    return mt == ARM64 || mt == ARM64X;
+  case ARM64EC:
+    return COFF::isArm64EC(mt) || mt == AMD64;
+  case ARM64X:
+    return COFF::isAnyArm64(mt) || mt == AMD64;
+  default:
+    return ctx.config.machine == mt;
+  }
+}
+
 void SymbolTable::addFile(InputFile *file) {
   log("Reading " + toString(file));
   if (file->lazy) {
@@ -56,7 +71,7 @@
   if (ctx.config.machine == IMAGE_FILE_MACHINE_UNKNOWN) {
     ctx.config.machine = mt;
     ctx.driver.addWinSysRootLibSearchPaths();
-  } else if (mt != IMAGE_FILE_MACHINE_UNKNOWN && ctx.config.machine != mt) {
+  } else if (!compatibleMachineType(ctx, mt)) {
     error(toString(file) + ": machine type " + machineToStr(mt) +
           " conflicts with " + machineToStr(ctx.config.machine));
     return;
Index: lld/test/COFF/arm64ec.test
===================================================================
--- lld/test/COFF/arm64ec.test
+++ lld/test/COFF/arm64ec.test
@@ -1,7 +1,9 @@
 REQUIRES: aarch64
 RUN: split-file %s %t.dir && cd %t.dir
 
+RUN: llvm-mc -filetype=obj -triple=aarch64-windows arm64-data-sym.s -o arm64-data-sym.obj
 RUN: llvm-mc -filetype=obj -triple=arm64ec-windows arm64ec-data-sym.s -o arm64ec-data-sym.obj
+RUN: llvm-mc -filetype=obj -triple=x86_64-windows x86_64-data-sym.s -o x86_64-data-sym.obj
 RUN: llvm-cvtres -machine:arm64x -out:arm64x-resource.obj %S/Inputs/resource.res
 
 RUN: lld-link -out:test.dll -machine:arm64ec arm64ec-data-sym.obj -dll -noentry
@@ -15,9 +17,40 @@
 RUN: llvm-readobj --file-headers test.dll | FileCheck -check-prefix=ARM64X-HEADER %s
 ARM64X-HEADER:      Machine: IMAGE_FILE_MACHINE_ARM64 (0xAA64)
 
+arm64x object files are allowed with -machine:arm64 as well
+RUN: lld-link -out:test.dll -machine:arm64 arm64x-resource.obj -dll -noentry
+
+RUN: lld-link -out:test.dll -machine:arm64ec arm64ec-data-sym.obj x86_64-data-sym.obj \
+RUN:          arm64x-resource.obj -dll -noentry
+RUN: llvm-readobj --file-headers test.dll | FileCheck -check-prefix=ARM64EC-HEADER %s
+
+RUN: llvm-readobj --hex-dump=.data test.dll | FileCheck -check-prefix=ARM64EC-DATA %s
+ARM64EC-DATA: 02020202 03030303
+
+RUN: lld-link -out:test.dll -machine:arm64x x86_64-data-sym.obj arm64-data-sym.obj \
+RUN:          arm64ec-data-sym.obj arm64x-resource.obj -dll -noentry
+RUN: llvm-readobj --file-headers test.dll | FileCheck -check-prefix=ARM64X-HEADER %s
+
+RUN: llvm-readobj --hex-dump=.data test.dll | FileCheck -check-prefix=ARM64X-DATA %s
+ARM64X-DATA: 03030303 01010101 02020202
+
 #--- arm64ec-data-sym.s
     .data
     .globl arm64ec_data_sym
     .p2align 2, 0x0
 arm64ec_data_sym:
     .word 0x02020202
+
+#--- arm64-data-sym.s
+    .data
+    .globl arm64_data_sym
+    .p2align 2, 0x0
+arm64_data_sym:
+    .word 0x01010101
+
+#--- x86_64-data-sym.s
+    .data
+    .globl x86_64_data_sym
+    .p2align 2, 0x0
+x86_64_data_sym:
+    .long 0x03030303