Index: llvm/lib/MC/MCDwarf.cpp
===================================================================
--- llvm/lib/MC/MCDwarf.cpp
+++ llvm/lib/MC/MCDwarf.cpp
@@ -514,6 +514,9 @@
     Directory = "";
   }
   assert(!FileName.empty());
+  // If any files have an MD5 checksum, they all must.
+  if (MCDwarfFiles.empty())
+    HasMD5 = (Checksum != nullptr);
   if (FileNumber == 0) {
     // File numbers start with 1 and/or after any file numbers
     // allocated by inline-assembler .file directives.
@@ -537,8 +540,8 @@
     return 0;
 
   // If any files have an MD5 checksum, they all must.
-  if (FileNumber > 1)
-    assert(HasMD5 == (Checksum != nullptr));
+  if (HasMD5 != (Checksum != nullptr))
+    return UINT_MAX;
 
   if (Directory.empty()) {
     // Separate the directory part from the basename of the FileName.
Index: llvm/lib/MC/MCParser/AsmParser.cpp
===================================================================
--- llvm/lib/MC/MCParser/AsmParser.cpp
+++ llvm/lib/MC/MCParser/AsmParser.cpp
@@ -3367,9 +3367,15 @@
     // we turn off -g option, directly use the existing debug info instead.
     if (getContext().getGenDwarfForAssembly())
       getContext().setGenDwarfForAssembly(false);
-    else if (getStreamer().EmitDwarfFileDirective(FileNumber, Directory,
-                                                  Filename, CKMem) == 0)
-      return Error(FileNumberLoc, "file number already allocated");
+    else {
+      FileNumber = getStreamer().EmitDwarfFileDirective(FileNumber, Directory,
+                                                        Filename, CKMem);
+      if (check(FileNumber == 0, FileNumberLoc,
+                "file number already allocated") ||
+          check(FileNumber == UINT_MAX, DirectiveLoc,
+                "inconsistent use of MD5 checksums"))
+        return true;
+    }
   }
 
   return false;
Index: llvm/test/MC/ELF/debug-md5-err.s
===================================================================
--- llvm/test/MC/ELF/debug-md5-err.s
+++ llvm/test/MC/ELF/debug-md5-err.s
@@ -19,3 +19,7 @@
 # Non-DWARF .file syntax with checksum.
 # CHECK: [[@LINE+1]]:{{[0-9]+}}: error: MD5 checksum specified, but no file number
         .file "baz" md5 "ffeeddccbbaa998877665544332211gg"
+
+# Inconsistent use of MD5 option. Note: .file 1 did not supply one.
+# CHECK: [[@LINE+1]]:{{[0-9]+}}: error: inconsistent use of MD5 checksums
+        .file 5 "bax" md5 "ffeeddccbbaa99887766554433221100"