diff --git a/src/librustc/session/config.rs b/src/librustc/session/config.rs
index bf532d9ccf9ed..b036238b0219d 100644
--- a/src/librustc/session/config.rs
+++ b/src/librustc/session/config.rs
@@ -1113,42 +1113,30 @@ pub fn build_session_options(matches: &getopts::Matches) -> Options {
     let target = matches.opt_str("target").unwrap_or(
         host_triple().to_string());
     let opt_level = {
-        if matches.opt_present("O") {
-            if cg.opt_level.is_some() {
-                early_error(error_format, "-O and -C opt-level both provided");
-            }
-            OptLevel::Default
-        } else {
-            match cg.opt_level {
-                None => OptLevel::No,
-                Some(0) => OptLevel::No,
-                Some(1) => OptLevel::Less,
-                Some(2) => OptLevel::Default,
-                Some(3) => OptLevel::Aggressive,
-                Some(arg) => {
-                    early_error(error_format, &format!("optimization level needs to be \
-                                                      between 0-3 (instead was `{}`)",
-                                                     arg));
-                }
+        match cg.opt_level {
+            None => OptLevel::No,
+            Some(0) => OptLevel::No,
+            Some(1) => OptLevel::Less,
+            Some(2) => OptLevel::Default,
+            Some(3) => OptLevel::Aggressive,
+            Some(arg) => {
+                early_error(error_format, &format!("optimization level needs to be \
+                                                    between 0-3 (instead was `{}`)",
+                                                   arg));
             }
         }
     };
     let debug_assertions = cg.debug_assertions.unwrap_or(opt_level == OptLevel::No);
     let gc = debugging_opts.gc;
-    let debuginfo = if matches.opt_present("g") {
-        if cg.debuginfo.is_some() {
-            early_error(error_format, "-g and -C debuginfo both provided");
-        }
-        FullDebugInfo
-    } else {
+    let debuginfo = {
         match cg.debuginfo {
             None | Some(0) => NoDebugInfo,
             Some(1) => LimitedDebugInfo,
             Some(2) => FullDebugInfo,
             Some(arg) => {
                 early_error(error_format, &format!("debug info level needs to be between \
-                                                  0-2 (instead was `{}`)",
-                                                 arg));
+                                                    0-2 (instead was `{}`)",
+                                                   arg));
             }
         }
     };
diff --git a/src/librustc_driver/lib.rs b/src/librustc_driver/lib.rs
index d8d1cf5a026b6..64bb72eb68d6a 100644
--- a/src/librustc_driver/lib.rs
+++ b/src/librustc_driver/lib.rs
@@ -159,7 +159,7 @@ pub fn run_compiler<'a>(args: &[String],
         }
     }}
 
-    let matches = match handle_options(args) {
+    let matches = match handle_options(args.to_vec()) {
         Some(matches) => matches,
         None => return (Ok(()), None),
     };
@@ -870,9 +870,9 @@ fn print_flag_list<T>(cmdline_opt: &str,
 ///
 /// So with all that in mind, the comments below have some more detail about the
 /// contortions done here to get things to work out correctly.
-pub fn handle_options(args: &[String]) -> Option<getopts::Matches> {
+pub fn handle_options(mut args: Vec<String>) -> Option<getopts::Matches> {
     // Throw away the first argument, the name of the binary
-    let args = &args[1..];
+    let _binary = args.remove(0);
 
     if args.is_empty() {
         // user did not write `-v` nor `-Z unstable-options`, so do not
@@ -881,6 +881,16 @@ pub fn handle_options(args: &[String]) -> Option<getopts::Matches> {
         return None;
     }
 
+    // Replace -O and -g with their equivalent -C options.
+    for i in 0..args.len() {
+        if args[i] == "-O" {
+            args[i] = "-Copt-level=2".to_string();
+        }
+        if args[i] == "-g" {
+            args[i] = "-Cdebuginfo=2".to_string();
+        }
+    }
+
     // Parse with *all* options defined in the compiler, we don't worry about
     // option stability here we just want to parse as much as possible.
     let all_groups: Vec<getopts::OptGroup> = config::rustc_optgroups()
diff --git a/src/test/run-make/multiple-options-parsing/Makefile b/src/test/run-make/multiple-options-parsing/Makefile
new file mode 100644
index 0000000000000..35444f32413a2
--- /dev/null
+++ b/src/test/run-make/multiple-options-parsing/Makefile
@@ -0,0 +1,14 @@
+-include ../tools.mk
+
+# Test that -O and -g can be used multiple times, together with their equivalent -C options.
+
+all:
+	$(RUSTC) -O -O dummy.rs
+	$(RUSTC) -O -C opt-level=2 dummy.rs
+	$(RUSTC) -C opt-level=2 -O dummy.rs
+	$(RUSTC) -C opt-level=2 -C opt-level=2 dummy.rs
+
+	$(RUSTC) -g -g dummy.rs
+	$(RUSTC) -g -C debuginfo=2 dummy.rs
+	$(RUSTC) -C debuginfo=2 -g dummy.rs
+	$(RUSTC) -C debuginfo=2 -C debuginfo=2 dummy.rs
diff --git a/src/test/run-make/multiple-options-parsing/dummy.rs b/src/test/run-make/multiple-options-parsing/dummy.rs
new file mode 100644
index 0000000000000..e06c0a5ec2a4c
--- /dev/null
+++ b/src/test/run-make/multiple-options-parsing/dummy.rs
@@ -0,0 +1,11 @@
+// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+fn main() {}