diff --git a/plugins/mips/mips.ml b/plugins/mips/mips.ml
index 2892476fc..c099a73f9 100644
--- a/plugins/mips/mips.ml
+++ b/plugins/mips/mips.ml
@@ -64,7 +64,7 @@ module Std = struct
             insn_name n in
         Error (Error.of_string str) in
     match String.Table.find lifters (Insn.name insn) with
-    | None -> Or_error.errorf "unknown instruction %s" insn_name
+    | None -> Ok []
     | Some lifter -> lift lifter
 
   module M32BE = struct
diff --git a/plugins/powerpc/powerpc.ml b/plugins/powerpc/powerpc.ml
index 02946b88d..aac5fde1c 100644
--- a/plugins/powerpc/powerpc.ml
+++ b/plugins/powerpc/powerpc.ml
@@ -53,7 +53,6 @@ module Std = struct
 
   let lift addr_size endian mem insn =
     let insn = Insn.of_basic insn in
-    let insn_name = Insn.name insn in
     let cpu = make_cpu addr_size endian mem  in
     let lift lifter =
       try
@@ -63,7 +62,7 @@ module Std = struct
       with
       | Failure str -> Error (Error.of_string str) in
     match Hashtbl.find lifters (Insn.name insn) with
-    | None -> Or_error.errorf "unknown instruction %s" insn_name
+    | None -> Ok []
     | Some lifter -> lift lifter
 
   module T32 = struct
diff --git a/plugins/x86/x86_backend.ml b/plugins/x86/x86_backend.ml
index df2b718c6..8c05c8e41 100644
--- a/plugins/x86/x86_backend.ml
+++ b/plugins/x86/x86_backend.ml
@@ -33,10 +33,7 @@ module Make (PR : PR) = struct
     let lift mem insn =
       let lift = search lifts insn in
       try match lift mem insn with
-        | Error err ->
-          warning "failed to lift %a - %a"
-            X86_utils.pp_insn (mem,insn) Error.pp err;
-          Error err
+        | Error err -> Error err
         | Ok bil as ok -> match Type.check bil with
           | Ok () -> ok
           | Error te ->
diff --git a/plugins/x86/x86_targets.ml b/plugins/x86/x86_targets.ml
index 0565ee89e..81d38145e 100644
--- a/plugins/x86/x86_targets.ml
+++ b/plugins/x86/x86_targets.ml
@@ -8,14 +8,12 @@ module AMD64L = X86_lifter.AMD64
 
 module IA32D = struct
   module CPU = IA32L.CPU
-  let lift _mem insn =
-    Or_error.error "unimplemented" insn Insn.sexp_of_t
+  let lift _mem _insn = Ok []
 end
 
 module AMD64D = struct
   module CPU = AMD64L.CPU
-  let lift _mem insn =
-    Or_error.error "unimplemented" insn Insn.sexp_of_t
+  let lift _mem _insn = Ok []
 end
 
 module IA32 = X86_backend.IA32.Make(IA32D)