diff --git a/gcc/config/mmix/mmix.c b/gcc/config/mmix/mmix.c
index 68f7ec3ab88..66e3d585a0a 100644
--- a/gcc/config/mmix/mmix.c
+++ b/gcc/config/mmix/mmix.c
@@ -318,6 +318,32 @@ mmix_option_override (void)
 	       (flag_pic > 1) ? "PIC" : "pic");
       flag_pic = 0;
     }
+
+  /* Don't bother with mmixal-compatible syntax if it's likely that a
+     certain format of the assembly is expected, like no new-line
+     after the .byte (or BYTE) parameter, when scanning debug-info
+     output, as happens in many places in the gcc testsuite.  The
+     dwarf2 output code (maybe others) takes a shortcut based on the
+     presence of certain assembler directives, instead of calling
+     assemble_integer.  Not worthwhile editing the test-cases:
+     mixed-syntax assembly output already looks too ugly for the
+     intent of being readable, and the resulting mix certainly fails
+     the intent of being compatible with mmixal.  See
+     varasm.c:default_file_start for this triple.  See also
+     mmix_assemble_integer.  */
+  if (flag_verbose_asm || flag_debug_asm || flag_dump_rtl_in_asm)
+    {
+      /* "Reinstate" the defaults from target-def.h that we
+	 overrode.  */
+      targetm.asm_out.byte_op = "\t.byte\t";
+      targetm.asm_out.aligned_op.hi = "\t.short\t";
+      targetm.asm_out.aligned_op.si = "\t.long\t";
+
+      /* Note that TARGET_ASM_ALIGNED_DI_OP is default NULL, so
+	 there's nothing to "reinstate".  Still, we add the universal
+	 default (with "recent" gas) for an address.  */
+      targetm.asm_out.aligned_op.di = "\t.dc.a\t";
+    }
 }
 
 /* INIT_EXPANDERS.  */
@@ -1379,10 +1405,11 @@ mmix_assemble_integer (rtx x, unsigned int size, int aligned_p)
 	   that's ok, because we can punt to generic functions.  We then
 	   pretend that aligned data isn't needed, so the usual .<pseudo>
 	   syntax is used (which works for aligned data too).  We actually
-	   *must* do that, since we say we don't have simple aligned
-	   pseudos, causing this function to be called.  We just try and
-	   keep as much compatibility as possible with mmixal syntax for
-	   normal cases (i.e. without GNU extensions and C only).  */
+	   *must* do that, since we (usually) say we don't have simple aligned
+	   pseudos, causing this function to be called.  See
+	   mmix_option_override for an exception.  We just try and keep as
+	   much compatibility as possible with mmixal syntax for normal
+	   cases (i.e. without GNU extensions and C only).  */
       case 1:
 	if (GET_CODE (x) != CONST_INT)
 	  {