diff --git a/src/comp/driver/rustc.rs b/src/comp/driver/rustc.rs
index 4dc58c04fe5a..be09a5907415 100644
--- a/src/comp/driver/rustc.rs
+++ b/src/comp/driver/rustc.rs
@@ -264,6 +264,7 @@ options:
     --test             build test harness
     --gc               garbage collect shared data (experimental/temporary)
     --stack-growth     perform stack checks (experimental)
+    --check-unsafe     disallow unsafe actions in non-unsafe functions (temporary option)
 
 ");
 }
@@ -322,6 +323,7 @@ fn build_session_options(match: getopts::match)
 
     let parse_only = opt_present(match, "parse-only");
     let no_trans = opt_present(match, "no-trans");
+    let check_unsafe = opt_present(match, "check-unsafe");
 
     let output_type =
         if parse_only || no_trans {
@@ -393,7 +395,8 @@ fn build_session_options(match: getopts::match)
           parse_only: parse_only,
           no_trans: no_trans,
           do_gc: do_gc,
-          stack_growth: stack_growth};
+          stack_growth: stack_growth,
+          check_unsafe: check_unsafe};
     ret sopts;
 }
 
@@ -432,7 +435,7 @@ fn opts() -> [getopts::opt] {
          optflag("no-typestate"), optflag("noverify"),
          optmulti("cfg"), optflag("test"),
          optflag("lib"), optflag("static"), optflag("gc"),
-         optflag("stack-growth")];
+         optflag("stack-growth"), optflag("check-unsafe")];
 }
 
 fn main(args: [str]) {
diff --git a/src/comp/driver/session.rs b/src/comp/driver/session.rs
index 1f3f9baab8a9..6ba2148e8a4c 100644
--- a/src/comp/driver/session.rs
+++ b/src/comp/driver/session.rs
@@ -41,7 +41,8 @@ type options =
      parse_only: bool,
      no_trans: bool,
      do_gc: bool,
-     stack_growth: bool};
+     stack_growth: bool,
+     check_unsafe: bool};
 
 type crate_metadata = {name: str, data: [u8]};
 
diff --git a/src/comp/middle/typeck.rs b/src/comp/middle/typeck.rs
index ec7c2537874e..26dcb5074da0 100644
--- a/src/comp/middle/typeck.rs
+++ b/src/comp/middle/typeck.rs
@@ -1524,11 +1524,13 @@ fn check_pat(fcx: @fn_ctxt, map: ast_util::pat_id_map, pat: @ast::pat,
 }
 
 fn require_unsafe(sess: session::session, f_purity: ast::purity, sp: span) {
-    alt f_purity {
-      ast::unsafe_fn. { ret; }
-      _ {
-        sess.span_fatal(sp, "Found unsafe expression in safe function decl");
-      }
+    if sess.get_opts().check_unsafe {
+        alt f_purity {
+          ast::unsafe_fn. { ret; }
+          _ {
+            sess.span_fatal(sp, "Found unsafe expression in safe function decl");
+          }
+        }
     }
 }
 
@@ -1547,17 +1549,22 @@ fn require_pure_call(ccx: @crate_ctxt, caller_purity: ast::purity,
     alt caller_purity {
       ast::unsafe_fn. { ret; }
       ast::impure_fn. {
+        let sess = ccx.tcx.sess;
         alt ccx.tcx.def_map.find(callee.id) {
           some(ast::def_fn(_, ast::unsafe_fn.)) {
-            ccx.tcx.sess.span_fatal
-                (sp, "safe function calls function marked unsafe");
+            if sess.get_opts().check_unsafe {
+                ccx.tcx.sess.span_fatal(
+                    sp,
+                    "safe function calls function marked unsafe");
+            }
           }
-          /* Temporarily disable until unsafe blocks parse!
           some(ast::def_native_fn(_)) {
-            ccx.tcx.sess.span_fatal
-                (sp, "native functions can only be invoked from unsafe code");
+            if sess.get_opts().check_unsafe {
+                ccx.tcx.sess.span_fatal(
+                    sp,
+                    "native functions can only be invoked from unsafe code");
+            }
           }
-          */
           _ {
           }
         }