diff --git a/src/librustc_binaryen/BinaryenWrapper.cpp b/src/librustc_binaryen/BinaryenWrapper.cpp
index d1095a7819d4a..55f11665f6d0b 100644
--- a/src/librustc_binaryen/BinaryenWrapper.cpp
+++ b/src/librustc_binaryen/BinaryenWrapper.cpp
@@ -14,6 +14,7 @@
 
 #include <stdint.h>
 #include <string>
+#include <sstream>
 #include <stdlib.h>
 
 #include "s2wasm.h"
@@ -24,6 +25,7 @@ using namespace wasm;
 
 struct BinaryenRustModule {
   BufferWithRandomAccess buffer;
+  std::string sourceMapJSON;
 };
 
 struct BinaryenRustModuleOptions {
@@ -36,6 +38,7 @@ struct BinaryenRustModuleOptions {
   bool ignoreUnknownSymbols;
   bool debugInfo;
   std::string startFunction;
+  std::string sourceMapUrl;
 
   BinaryenRustModuleOptions() :
     globalBase(0),
@@ -46,7 +49,8 @@ struct BinaryenRustModuleOptions {
     importMemory(false),
     ignoreUnknownSymbols(false),
     debugInfo(false),
-    startFunction("")
+    startFunction(""),
+    sourceMapUrl("")
   {}
 
 };
@@ -73,6 +77,12 @@ BinaryenRustModuleOptionsSetStart(BinaryenRustModuleOptions *options,
   options->startFunction = start;
 }
 
+extern "C" void
+BinaryenRustModuleOptionsSetSourceMapUrl(BinaryenRustModuleOptions *options,
+                                         char *sourceMapUrl) {
+  options->sourceMapUrl = sourceMapUrl;
+}
+
 extern "C" void
 BinaryenRustModuleOptionsSetStackAllocation(BinaryenRustModuleOptions *options,
                                             uint64_t stack) {
@@ -106,12 +116,20 @@ BinaryenRustModuleCreate(const BinaryenRustModuleOptions *options,
   {
     WasmBinaryWriter writer(&linker.getOutput().wasm, ret->buffer, options->debug);
     writer.setNamesSection(options->debugInfo);
-    // FIXME: support source maps?
-    // writer.setSourceMap(sourceMapStream.get(), sourceMapUrl);
+
+    std::unique_ptr<std::ostringstream> sourceMapStream = nullptr;
+    {
+      sourceMapStream = make_unique<std::ostringstream>();
+      writer.setSourceMap(sourceMapStream.get(), options->sourceMapUrl);
+    }
 
     // FIXME: support symbol maps?
     // writer.setSymbolMap(symbolMap);
     writer.write();
+
+    if (sourceMapStream) {
+      ret->sourceMapJSON = sourceMapStream->str();
+    }
   }
   return ret.release();
 }
@@ -126,6 +144,16 @@ BinaryenRustModuleLen(const BinaryenRustModule *M) {
   return M->buffer.size();
 }
 
+extern "C" const char*
+BinaryenRustModuleSourceMapPtr(const BinaryenRustModule *M) {
+  return M->sourceMapJSON.data();
+}
+
+extern "C" size_t
+BinaryenRustModuleSourceMapLen(const BinaryenRustModule *M) {
+  return M->sourceMapJSON.length();
+}
+
 extern "C" void
 BinaryenRustModuleFree(BinaryenRustModule *M) {
   delete M;
diff --git a/src/librustc_binaryen/lib.rs b/src/librustc_binaryen/lib.rs
index 6c7feb6a7a9d3..36174e11ba04a 100644
--- a/src/librustc_binaryen/lib.rs
+++ b/src/librustc_binaryen/lib.rs
@@ -51,6 +51,15 @@ impl Module {
             slice::from_raw_parts(ptr, len)
         }
     }
+
+    /// Returns the data of the source map JSON.
+    pub fn source_map(&self) -> &[u8] {
+        unsafe {
+            let ptr = BinaryenRustModuleSourceMapPtr(self.ptr);
+            let len = BinaryenRustModuleSourceMapLen(self.ptr);
+            slice::from_raw_parts(ptr, len)
+        }
+    }
 }
 
 impl Drop for Module {
@@ -94,6 +103,15 @@ impl ModuleOptions {
         self
     }
 
+    /// Configures a `sourceMappingURL` custom section value for the module.
+    pub fn source_map_url(&mut self, url: &str) -> &mut Self {
+        let url = CString::new(url).unwrap();
+        unsafe {
+            BinaryenRustModuleOptionsSetSourceMapUrl(self.ptr, url.as_ptr());
+        }
+        self
+    }
+
     /// Configures how much stack is initially allocated for the module. 1MB is
     /// probably good enough for now.
     pub fn stack(&mut self, amt: u64) -> &mut Self {
@@ -130,6 +148,8 @@ extern {
         -> *mut BinaryenRustModule;
     fn BinaryenRustModulePtr(module: *const BinaryenRustModule) -> *const u8;
     fn BinaryenRustModuleLen(module: *const BinaryenRustModule) -> usize;
+    fn BinaryenRustModuleSourceMapPtr(module: *const BinaryenRustModule) -> *const u8;
+    fn BinaryenRustModuleSourceMapLen(module: *const BinaryenRustModule) -> usize;
     fn BinaryenRustModuleFree(module: *mut BinaryenRustModule);
 
     fn BinaryenRustModuleOptionsCreate()
@@ -138,6 +158,8 @@ extern {
                                              debuginfo: bool);
     fn BinaryenRustModuleOptionsSetStart(module: *mut BinaryenRustModuleOptions,
                                          start: *const libc::c_char);
+    fn BinaryenRustModuleOptionsSetSourceMapUrl(module: *mut BinaryenRustModuleOptions,
+                                                sourceMapUrl: *const libc::c_char);
     fn BinaryenRustModuleOptionsSetStackAllocation(
         module: *mut BinaryenRustModuleOptions,
         stack: u64,
diff --git a/src/librustc_trans/back/write.rs b/src/librustc_trans/back/write.rs
index a013af7a4600e..7a194a37c9c55 100644
--- a/src/librustc_trans/back/write.rs
+++ b/src/librustc_trans/back/write.rs
@@ -748,7 +748,10 @@ unsafe fn codegen(cgcx: &CodegenContext,
 
         if asm2wasm && config.emit_obj {
             let assembly = cgcx.output_filenames.temp_path(OutputType::Assembly, module_name);
-            binaryen_assemble(cgcx, diag_handler, &assembly, &obj_out);
+            let suffix = ".wasm.map"; // FIXME use target suffix
+            let map = cgcx.output_filenames.path(OutputType::Exe)
+                .with_extension(&suffix[1..]);
+            binaryen_assemble(cgcx, diag_handler, &assembly, &obj_out, &map);
             timeline.record("binaryen");
 
             if !config.emit_asm {
@@ -795,7 +798,8 @@ unsafe fn codegen(cgcx: &CodegenContext,
 fn binaryen_assemble(cgcx: &CodegenContext,
                      handler: &Handler,
                      assembly: &Path,
-                     object: &Path) {
+                     object: &Path,
+                     map: &Path) {
     use rustc_binaryen::{Module, ModuleOptions};
 
     let input = fs::read(&assembly).and_then(|contents| {
@@ -804,6 +808,8 @@ fn binaryen_assemble(cgcx: &CodegenContext,
     let mut options = ModuleOptions::new();
     if cgcx.debuginfo != config::NoDebugInfo {
         options.debuginfo(true);
+        let map_file_name = map.file_name().unwrap();
+        options.source_map_url(map_file_name.to_str().unwrap());
     }
     if cgcx.crate_types.contains(&config::CrateTypeExecutable) {
         options.start("main");
@@ -815,7 +821,13 @@ fn binaryen_assemble(cgcx: &CodegenContext,
             .map_err(|e| io::Error::new(io::ErrorKind::Other, e))
     });
     let err = assembled.and_then(|binary| {
-        fs::write(&object, binary.data())
+        fs::write(&object, binary.data()).and_then(|()| {
+            if cgcx.debuginfo != config::NoDebugInfo {
+                fs::write(map, binary.source_map())
+            } else {
+                Ok(())
+            }
+        })
     });
     if let Err(e) = err {
         handler.err(&format!("failed to run binaryen assembler: {}", e));