diff --git a/runtime/llvm-runtime.lisp b/runtime/llvm-runtime.lisp
index 291bd2d..a9c0a31 100644
--- a/runtime/llvm-runtime.lisp
+++ b/runtime/llvm-runtime.lisp
@@ -125,7 +125,7 @@ PERSONALITY is bound to the context's personality object."
 (define-compiler-macro sign-extend (&whole whole value width)
   (declare (ignorable whole))
   (cond
-    #+sbcl
+    #+(and sbcl (not ppc64))
     ((member width '(8 16 32))
      `(sb-vm::sign-extend ,value ,width))
     ((integerp width)
@@ -354,7 +354,7 @@ PERSONALITY is bound to the context's personality object."
         (t
          `(sign-extend ,value ,input-size)))
   #+sbcl
-  `(sign-extend ,value ,size))
+  `(sign-extend ,value ,input-size))
 
 (define-integer-conversion-op zext (value size)
   value)