diff --git a/scripts/fuzz_opt.py b/scripts/fuzz_opt.py
index bf0892be681..66a01d86a1d 100755
--- a/scripts/fuzz_opt.py
+++ b/scripts/fuzz_opt.py
@@ -2107,8 +2107,9 @@ def get_relevant_lines(wat):
 # This reads wasm+js combinations from the test/js_wasm directory, so as new
 # testcases are added there, this will fuzz them.
 #
-# Note that bugs found by this fuzzer require BINARYEN_TRUST_GIVEN_WASM=1 in the
-# env for reduction. TODO: simplify this
+# Note that bugs found by this fuzzer require BINARYEN_PIEJS_WASM=1 in the
+# env for reduction. TODO: simplify this, and show it when the fuzzer prints out
+# the command to reduce.
 class PreserveImportsExportsJS(TestCaseHandler):
     frequency = 1
 
@@ -2116,11 +2117,12 @@ def handle_pair(self, input, before_wasm, after_wasm, opts):
         try:
             self.do_handle_pair(input, before_wasm, after_wasm, opts)
         except Exception as e:
-            if not os.environ.get('BINARYEN_TRUST_GIVEN_WASM'):
-                # We errored, and we were not given a wasm file to trust as we
-                # reduce, so this is the first time we hit an error. Save the
+            if not os.environ.get('BINARYEN_PIEJS_WASM'):
+                # We errored, and we were not in the middle of reducing a given
+                # file, so this is the first time we hit an error. Save the
                 # pre wasm file, the one we began with, as `before_wasm`, so
                 # that the reducer will make us proceed exactly from there.
+                print(f'copying {self.pre_wasm} to original for reduction: {before_wasm}')
                 shutil.copyfile(self.pre_wasm, before_wasm)
             raise e
 
@@ -2151,9 +2153,9 @@ def do_handle_pair(self, input, before_wasm, after_wasm, opts):
 
         # Make sure the testcase runs by itself - there should be no invalid
         # testcases.
-        original_wasm = 'orig.wasm'
-        run([in_bin('wasm-opt'), wat_file, '-o', original_wasm] + FEATURE_OPTS)
-        D8().run_js(js_file, original_wasm)
+        initial_wasm = 'initial.wasm'
+        run([in_bin('wasm-opt'), wat_file, '-o', initial_wasm] + FEATURE_OPTS)
+        D8().run_js(js_file, initial_wasm)
 
         # Modify the initial wat to get the pre-optimizations wasm.
         pre_wasm = abspath('pre.wasm')
@@ -2172,9 +2174,10 @@ def do_handle_pair(self, input, before_wasm, after_wasm, opts):
         # If we were given a wasm file, use that instead of all the above. We
         # do this now, after creating pre_wasm, because we still need to consume
         # all the randomness normally.
-        if os.environ.get('BINARYEN_TRUST_GIVEN_WASM'):
-            print('using given wasm', before_wasm)
-            pre_wasm = before_wasm
+        given_wasm = os.environ.get('BINARYEN_PIEJS_WASM')
+        if given_wasm:
+            print('using BINARYEN_PIEJS_WASM', given_wasm)
+            pre_wasm = given_wasm
 
         # Pick a vm and run before we optimize the wasm.
         vms = [
@@ -2866,7 +2869,12 @@ def get_random_opts():
             # longer working on the original test case but modified one, which
             # is likely to be called within wasm-reduce script itself, so
             # original.wasm and reduce.sh should not be overwritten.
-            if not given_wasm:
+            #
+            # We must also consider the case of BINARYEN_PIEJS_WASM as us being
+            # given a wasm file. We are given one in this case, but only for
+            # that particular fuzzer, hence it is passed in through an env var
+            # and not the usual mechanism.
+            if not given_wasm and not os.environ.get('BINARYEN_PIEJS_WASM'):
                 # We can't do this if a.wasm doesn't exist, which can be the
                 # case if we failed to even generate the wasm.
                 if not os.path.exists('a.wasm'):
@@ -2892,6 +2900,7 @@ def get_random_opts():
                 # the side, so that we can autoreduce using the name "a.wasm"
                 # which we use internally)
                 original_wasm = abspath('original.wasm')
+                print(f'copying a.wasm to original for reduction: {original_wasm}')
                 shutil.copyfile('a.wasm', original_wasm)
                 # write out a useful reduce.sh
                 auto_init = ''
@@ -2913,14 +2922,21 @@ def get_random_opts():
 
 echo "The following value should be >0:"
 
-if [ -z "$BINARYEN_FIRST_WASM" ]; then
-  # run the command normally
-  ./scripts/fuzz_opt.py {auto_init} --binaryen-bin {binaryen_bin} {seed} {temp_wasm} > o 2> e
-else
-  # BINARYEN_FIRST_WASM was provided so we should actually reduce the *second*
+if [ -n "$BINARYEN_FIRST_WASM" ]; then
+  # BINARYEN_FIRST_WASM was provided, so we should actually reduce the *second*
   # file. pass the first one in as the main file, and use the env var for the
   # second.
   BINARYEN_SECOND_WASM={temp_wasm} ./scripts/fuzz_opt.py {auto_init} --binaryen-bin {binaryen_bin} {seed} $BINARYEN_FIRST_WASM > o 2> e
+elif [ -n "$BINARYEN_PIEJS_WASM" ]; then
+  # BINARYEN_PIEJS_WASM was provided, so we want to give that fuzzer the actual
+  # file we are reducing. All other fuzzers should *not* be given this file, as
+  # it may not even be valid for them (that fuzzer uses special js/wasm
+  # combinations). We therefore provide the temp wasm file to BINARYEN_PIEJS_WASM
+  # and *not* as a Python argument after the seed.
+  BINARYEN_PIEJS_WASM={temp_wasm} ./scripts/fuzz_opt.py {auto_init} --binaryen-bin {binaryen_bin} {seed} > o 2> e
+else
+  # run the command normally
+  ./scripts/fuzz_opt.py {auto_init} --binaryen-bin {binaryen_bin} {seed} {temp_wasm} > o 2> e
 fi
 
 echo "  " $?
@@ -2948,8 +2964,7 @@ def get_random_opts():
 #
 # You may also need to add  --timeout 5  or such if the testcase is a slow one.
 #
-# If the testcase handler uses a second wasm file, you may be able to reduce it
-# using BINARYEN_SECOND_WASM.
+# For reducing Two and PreserveImportsExportsJS, see the comments there.
 #
 ''')