diff --git a/src/parseTools.js b/src/parseTools.js
index a4ce78812d9b0..d6c47b6f2edbd 100644
--- a/src/parseTools.js
+++ b/src/parseTools.js
@@ -213,6 +213,12 @@ function makeInlineCalculation(expression, value, tempVar) {
 // value, represented by a low and high i32 pair.
 // Will suffer from rounding and truncation.
 function splitI64(value) {
+  if (WASM_BIGINT) {
+    // Nothing to do: just make sure it is a BigInt (as it must be of that
+    // type, to be sent into wasm).
+    return `BigInt(${value})`;
+  }
+
   // general idea:
   //
   //  $1$0 = ~~$d >>> 0;
@@ -229,7 +235,6 @@ function splitI64(value) {
   // For negatives, we need to ensure a -1 if the value is overall negative,
   // even if not significant negative component
 
-  assert(!WASM_BIGINT, 'splitI64 should not be used when WASM_BIGINT is enabled');
   const low = value + '>>>0';
   const high = makeInlineCalculation(
       asmCoercion('Math.abs(VALUE)', 'double') + ' >= ' + asmEnsureFloat('1', 'double') + ' ? ' +
@@ -886,15 +891,10 @@ function receiveI64ParamAsI53(name, onError) {
 }
 
 function receiveI64ParamAsI53Unchecked(name) {
-  if (WASM_BIGINT) return `${name} = Number(${name});`;
-  return `var ${name} = convertI32PairToI53(${name}_low, ${name}_high);`;
-}
-
-function sendI64Argument(low, high) {
   if (WASM_BIGINT) {
-    return 'BigInt(low) | (BigInt(high) << 32n)';
+    return `${name} = Number(${name});`;
   }
-  return low + ', ' + high;
+  return `var ${name} = convertI32PairToI53(${name}_low, ${name}_high);`;
 }
 
 // Any function called from wasm64 may have bigint args, this function takes
diff --git a/test/core/js_library_i64_params.c b/test/core/js_library_i64_params.c
index 4f0cc33ad98a5..764fc20b0e490 100644
--- a/test/core/js_library_i64_params.c
+++ b/test/core/js_library_i64_params.c
@@ -1,4 +1,5 @@
 #include <assert.h>
+#include <emscripten.h>
 #include <stdio.h>
 
 #define MAX_SAFE_INTEGER (1ll<<53)
@@ -8,6 +9,11 @@
 
 int64_t jscall(int64_t arg);
 
+EMSCRIPTEN_KEEPALIVE
+void called_from_js(uint64_t arg) {
+  printf("called_from_js with: %lld\n", arg);
+}
+
 void check_ok(int64_t val) {
   printf("checking: %lld\n", val);
   int64_t rtn = jscall(val);
@@ -25,7 +31,11 @@ void check_invalid(int64_t val) {
 }
 
 int main() {
+  check_ok(0);
+  check_ok(1);
+  check_ok(-1);
   check_ok(42);
+  check_ok(-42);
   check_ok(MAX_SAFE_INTEGER/2);
   check_ok(MIN_SAFE_INTEGER/2);
   check_ok(MAX_SAFE_INTEGER);
diff --git a/test/core/js_library_i64_params.js b/test/core/js_library_i64_params.js
index 28a00cf1174df..6c9f886c81e78 100644
--- a/test/core/js_library_i64_params.js
+++ b/test/core/js_library_i64_params.js
@@ -4,6 +4,9 @@ TestLibrary = {
   jscall: function({{{ defineI64Param('foo') }}}) {
     {{{ receiveI64ParamAsI53('foo', `(err('overflow'), ${makeReturn64('42')})`) }}}
     err('js:got:       ' + foo);
+
+    _called_from_js({{{ splitI64("foo") }}});
+
     if (foo < 0)
       var rtn = Math.ceil(foo / 2);
     else
diff --git a/test/core/js_library_i64_params.out b/test/core/js_library_i64_params.out
index 8f1d9b62dcc6b..26db9827949b3 100644
--- a/test/core/js_library_i64_params.out
+++ b/test/core/js_library_i64_params.out
@@ -1,25 +1,54 @@
+checking: 0
+js:got:       0
+called_from_js with: 0
+js:returning: 0
+got:      0
+expected: 0
+checking: 1
+js:got:       1
+called_from_js with: 1
+js:returning: 0
+got:      0
+expected: 0
+checking: -1
+js:got:       -1
+called_from_js with: -1
+js:returning: 0
+got:      0
+expected: 0
 checking: 42
 js:got:       42
+called_from_js with: 42
 js:returning: 21
 got:      21
 expected: 21
+checking: -42
+js:got:       -42
+called_from_js with: -42
+js:returning: -21
+got:      -21
+expected: -21
 checking: 4503599627370496
 js:got:       4503599627370496
+called_from_js with: 4503599627370496
 js:returning: 2251799813685248
 got:      2251799813685248
 expected: 2251799813685248
 checking: -4503599627370496
 js:got:       -4503599627370496
+called_from_js with: -4503599627370496
 js:returning: -2251799813685248
 got:      -2251799813685248
 expected: -2251799813685248
 checking: 9007199254740992
 js:got:       9007199254740992
+called_from_js with: 9007199254740992
 js:returning: 4503599627370496
 got:      4503599627370496
 expected: 4503599627370496
 checking: -9007199254740992
 js:got:       -9007199254740992
+called_from_js with: -9007199254740992
 js:returning: -4503599627370496
 got:      -4503599627370496
 expected: -4503599627370496