diff --git a/src/lib/linux_os.rs b/src/lib/linux_os.rs
index 6695377db398..81b4781a8737 100644
--- a/src/lib/linux_os.rs
+++ b/src/lib/linux_os.rs
@@ -57,6 +57,10 @@ fn target_os() -> str {
     ret "linux";
 }
 
+fn dylib_filename(str base) -> str {
+    ret "lib" + base + ".so";
+}
+
 fn pipe() -> tup(int, int) {
     let vec[mutable int] fds = vec(mutable 0, 0);
     check(os.libc.pipe(_vec.buf[mutable int](fds)) == 0);
diff --git a/src/lib/macos_os.rs b/src/lib/macos_os.rs
index fff528975c09..c2a1bee3ed9a 100644
--- a/src/lib/macos_os.rs
+++ b/src/lib/macos_os.rs
@@ -54,6 +54,10 @@ fn target_os() -> str {
     ret "macos";
 }
 
+fn dylib_filename(str base) -> str {
+    ret "lib" + base + ".dylib";
+}
+
 fn pipe() -> tup(int, int) {
     let vec[mutable int] fds = vec(mutable 0, 0);
     check(os.libc.pipe(_vec.buf[mutable int](fds)) == 0);
diff --git a/src/lib/win32_os.rs b/src/lib/win32_os.rs
index 56c65bfcc800..6885be243e44 100644
--- a/src/lib/win32_os.rs
+++ b/src/lib/win32_os.rs
@@ -42,6 +42,10 @@ fn target_os() -> str {
     ret "win32";
 }
 
+fn dylib_filename(str base) -> str {
+    ret base + ".dll";
+}
+
 fn pipe() -> tup(int, int) {
     let vec[mutable int] fds = vec(mutable 0, 0);
     check(os.libc._pipe(_vec.buf[mutable int](fds), 1024u,