diff --git a/src/support.js b/src/support.js
index 4e5a18f98..0d8efe1b9 100644
--- a/src/support.js
+++ b/src/support.js
@@ -221,7 +221,7 @@ function loadDynamicLibrary(lib, flags) {
     if (libModule.dynamicLibraries) {
       if (flags.loadAsync) {
         return Promise.all(libModule.dynamicLibraries.map(function(dynNeeded) {
-          return loadDynamicLibrary(dynNeeed, flags);
+          return loadDynamicLibrary(dynNeeded, flags);
         })).then(function() {
           return libModule;
         });
diff --git a/tests/test_core.py b/tests/test_core.py
index 97f27f737..6cdcd241a 100644
--- a/tests/test_core.py
+++ b/tests/test_core.py
@@ -4096,16 +4096,18 @@ def test_dylink_dso_needed(self):
     self.set_setting('TOTAL_MEMORY', 64 * 1024 * 1024)  # XXX default 16MB is not enough
 
     so = '.wasm' if self.is_wasm() else '.js'
+
     def ccshared(src, linkto=[]):
-      run_process([PYTHON, EMCC, src, '-s', 'SIDE_MODULE=1', '-o', os.path.splitext(src)[0]+so] \
-          + self.get_emcc_args() + ['-s', 'RUNTIME_LINKED_LIBS='+str(linkto)])
+      cmdv = [PYTHON, EMCC, src, '-s', 'SIDE_MODULE=1', '-o', os.path.splitext(src)[0] + so]
+      cmdv += self.get_emcc_args() + ['-s', 'RUNTIME_LINKED_LIBS=' + str(linkto)]
+      run_process(cmdv)
 
     ccshared('liba.cpp')
-    ccshared('libb.cpp', ['liba'+so])
-    ccshared('libc.cpp', ['liba'+so])
+    ccshared('libb.cpp', ['liba' + so])
+    ccshared('libc.cpp', ['liba' + so])
 
     self.set_setting('MAIN_MODULE', 1)
-    self.set_setting('RUNTIME_LINKED_LIBS', ['libb'+so, 'libc'+so])
+    self.set_setting('RUNTIME_LINKED_LIBS', ['libb' + so, 'libc' + so])
     self.do_run(r'''
       void bfunc();
       void cfunc();
@@ -4115,8 +4117,8 @@ def ccshared(src, linkto=[]):
         cfunc();
         return 0;
       }
-    ''',
-    'a: loaded\na: b (prev: (null))\na: c (prev: b)\n')
+      ''',
+                'a: loaded\na: b (prev: (null))\na: c (prev: b)\n')
 
     self.set_setting('RUNTIME_LINKED_LIBS', [])
     self.emcc_args += ['--embed-file', '.@/']
@@ -4145,7 +4147,7 @@ def ccshared(src, linkto=[]):
         return 0;
       }
     ''' % locals(),
-    'a: loaded\na: b (prev: (null))\na: c (prev: b)\n')
+                'a: loaded\na: b (prev: (null))\na: c (prev: b)\n')
 
   @needs_dlfcn
   def test_dylink_dot_a(self):

diff --git a/src/support.js b/src/support.js
index 0d8efe1b9..f67b1df41 100644
--- a/src/support.js
+++ b/src/support.js
@@ -86,6 +86,10 @@ var asm2wasmImports = { // special asm2wasm imports
 #if RELOCATABLE
 // dynamic linking
 var $LDSO = {
+  // next free handle to use for a loaded dso.
+  // (handle=0 is avoided as it means "error" in dlopen)
+  nextHandle: 1,
+
   loadedLibs: {         // handle -> dso [refcount, name, module, global]
     // program itself
     // XXX uglifyjs fails on "[-1]: {"
@@ -165,10 +169,7 @@ function loadDynamicLibrary(lib, flags) {
   }
 
   // allocate new DSO & handle
-  handle = 1
-  for (var key in $LDSO.loadedLibs) { // not all browsers support Object.keys()
-    if ($LDSO.loadedLibs.hasOwnProperty(key)) handle++;
-  }
+  handle = $LDSO.nextHandle++;
   dso = {
     refcount: flags.nodelete ? Infinity : 1,
     name:     lib,
@@ -294,7 +295,7 @@ function loadDynamicLibrary(lib, flags) {
     }
   }
 
-  // module for lib is loaded - update the dso
+  // module for lib is loaded - update the dso & global namespace
   function moduleLoaded(libModule) {
     if (dso.global) {
       mergeLibSymbols(libModule);
@@ -414,7 +415,7 @@ function loadWebAssemblyModule(binary, flags) {
         env[x] = Module[x];
       }
     }
-    // TODO kill vvv (it will likely be not needed if we require that if A wants
+    // TODO kill ↓↓↓ (it will likely be not needed if we require that if A wants
     // symbols from B it has to link to B explicitly: similarly to -Wl,--no-undefined)
     //
     // wasm dynamic libraries are pure wasm, so they cannot assist in
diff --git a/tests/test_core.py b/tests/test_core.py
index 6cdcd241a..7c0508e58 100644
--- a/tests/test_core.py
+++ b/tests/test_core.py
@@ -3290,6 +3290,63 @@ def zzztest_dlfcn_exceptions(self): # TODO: make this work. need to forward temp
 ok
 ''')
 
+  @needs_dlfcn
+  def test_dlfcn_handle_alloc(self):
+    # verify that dlopen does not allocate already used handles
+    dirname = self.get_dir()
+
+    def indir(name):
+      return os.path.join(dirname, name)
+
+    libecho = r'''
+      #include <stdio.h>
+
+      static struct %(libname)s {
+        %(libname)s() {
+          puts("%(libname)s: loaded");
+        }
+      } _;
+    '''
+
+    self.prep_dlfcn_lib()
+    self.build_dlfcn_lib(libecho % {'libname': 'a'}, dirname, indir('a.cpp'))
+    shutil.move(indir('liblib.so'), indir('liba.so'))
+    self.build_dlfcn_lib(libecho % {'libname': 'b'}, dirname, indir('b.cpp'))
+    shutil.move(indir('liblib.so'), indir('libb.so'))
+
+    self.set_setting('MAIN_MODULE', 1)
+    self.set_setting('SIDE_MODULE', 0)
+    self.set_setting('EXPORT_ALL', 1)
+    self.emcc_args += ['--embed-file', '.@/']
+
+    # XXX in wasm each lib load currently takes 5MB; default TOTAL_MEMORY=16MB is thus not enough
+    self.set_setting('TOTAL_MEMORY', 32 * 1024 * 1024)
+
+    src = r'''
+      #include <dlfcn.h>
+      #include <assert.h>
+      #include <stddef.h>
+
+      int main() {
+        void *liba, *libb, *liba2;
+        int err;
+
+        liba = dlopen("liba.so", RTLD_NOW);
+        assert(liba != NULL);
+        libb = dlopen("libb.so", RTLD_NOW);
+        assert(liba != NULL);
+
+        err = dlclose(liba);
+        assert(!err);
+
+        liba2 = dlopen("liba.so", RTLD_NOW);
+        assert(liba2 != libb);
+
+        return 0;
+      }
+      '''
+    self.do_run(src, 'a: loaded\nb: loaded\na: loaded\n')
+
   def dylink_test(self, main, side, expected, header=None, main_emcc_args=[], force_c=False, need_reverse=True, auto_load=True):
     # shared settings
     self.set_setting('EXPORT_ALL', 1)
@@ -4052,7 +4109,8 @@ def test_dylink_dso_needed(self):
     #          B
     #   main <   > A
     #          C
-    open('liba.cpp', 'w').write(r'''
+    with open('liba.cpp', 'w') as f:
+      f.write(r'''
         #include <stdio.h>
         #include <emscripten.h>
 
@@ -4073,7 +4131,8 @@ def test_dylink_dso_needed(self):
         static ainit _;
       ''')
 
-    open('libb.cpp', 'w').write(r'''
+    with open('libb.cpp', 'w') as f:
+      f.write(r'''
         #include <emscripten.h>
 
         void afunc(const char *s);
@@ -4083,7 +4142,8 @@ def test_dylink_dso_needed(self):
         }
       ''')
 
-    open('libc.cpp', 'w').write(r'''
+    with open('libc.cpp', 'w') as f:
+      f.write(r'''
         #include <emscripten.h>
 
         void afunc(const char *s);
@@ -4093,7 +4153,8 @@ def test_dylink_dso_needed(self):
         }
       ''')
 
-    self.set_setting('TOTAL_MEMORY', 64 * 1024 * 1024)  # XXX default 16MB is not enough
+    # XXX in wasm each lib load currently takes 5MB; default TOTAL_MEMORY=16MB is thus not enough
+    self.set_setting('TOTAL_MEMORY', 32 * 1024 * 1024)
 
     so = '.wasm' if self.is_wasm() else '.js'
 
diff --git a/tools/shared.py b/tools/shared.py
index a6f49f2d1..03cb7b544 100644
--- a/tools/shared.py
+++ b/tools/shared.py
@@ -2994,6 +2994,9 @@ def make_shared_library(js_file, wasm_file, needed_dynlibs):
     #
     #   dynlib_name_len             varuint32       ; length of dynlib_name_str in bytes
     #   dynlib_name_str             bytes           ; name of a needed dynamic library: valid UTF-8 byte sequence
+    #
+    # a proposal has been filed to include the extension into "dylink" specification:
+    # https://github.com/WebAssembly/tool-conventions/pull/77
     contents += WebAssembly.lebify(len(needed_dynlibs))
     for dyn_needed in needed_dynlibs:
         dyn_needed = asbytes(dyn_needed)

diff --git a/tests/test_browser.py b/tests/test_browser.py
index f038f14f1..1e59525ff 100644
--- a/tests/test_browser.py
+++ b/tests/test_browser.py
@@ -3238,6 +3238,9 @@ def test_webidl(self):
 
   @requires_sync_compilation
   def test_dynamic_link(self):
+    # verify that dynamic linking works in all kinds of in-browser environments.
+    #
+    # main -> side -> side2
     open('pre.js', 'w').write('''
       Module.dynamicLibraries = ['side.wasm'];
   ''')
@@ -3275,7 +3278,6 @@ def test_dynamic_link(self):
     open('side2.cpp', 'w').write(r'''
       #include <stdlib.h>
       #include <string.h>
-      char *side2(const char *data);
       char *side2(const char *data) {
         char *ret = (char*)malloc(strlen(data)+1);
         strcpy(ret, data);
diff --git a/tools/shared.py b/tools/shared.py
index bc05815fe..1c7c0e56d 100644
--- a/tools/shared.py
+++ b/tools/shared.py
@@ -2977,9 +2977,9 @@ def make_shared_library(js_file, wasm_file, needed_dynlibs):
     # https://github.com/WebAssembly/tool-conventions/pull/77
     contents += WebAssembly.lebify(len(needed_dynlibs))
     for dyn_needed in needed_dynlibs:
-        dyn_needed = asbytes(dyn_needed)
-        contents += WebAssembly.lebify(len(dyn_needed))
-        contents += dyn_needed
+      dyn_needed = asbytes(dyn_needed)
+      contents += WebAssembly.lebify(len(dyn_needed))
+      contents += dyn_needed
 
     size = len(name) + len(contents)
     f.write(WebAssembly.lebify(size))