diff --git a/bend2/comp.ts b/bend2/comp.ts
index 64dbc33669..2433237ca3 100644
--- a/bend2/comp.ts
+++ b/bend2/comp.ts
@@ -6045,8 +6045,8 @@ function f32_from_bits(u) {
 
 function f32_read(s) {
   const re = /^[\t\n\v\f\r ]*[+-]?((\d+(?:\.\d*)?|\.\d+)(e[+-]?\d+)?|inf(inity)?|nan)$/i;
-  const v = f32_round(s.replace(/inf\w*/i, "Infinity"));
-  return re.test(s) ? {$: "Some", value: v} : {$: "None"};
+  return re.test(s) ? {$: "Some", value: f32_round(
+    s.replace(/inf\w*/i, "Infinity"))} : {$: "None"};
 }
 
 const f32_round = ${Bend.f32_round};
diff --git a/tests/run/f32_read_long_invalid.bend b/tests/run/f32_read_long_invalid.bend
index 95e7dca347..080d3763d9 100644
--- a/tests/run/f32_read_long_invalid.bend
+++ b/tests/run/f32_read_long_invalid.bend
@@ -1,14 +1,15 @@
 # The JS reader must reject a long integer with an invalid suffix without
-# splitting its digits between two overlapping repetitions. Build it with
-# a tail-recursive accumulator so string construction does not exhaust the stack.
+# splitting its digits between two overlapping repetitions. A long decimal
+# midpoint with a trailing space must be rejected before exact rounding.
+# Build both with a tail-recursive accumulator to avoid exhausting the stack.
 import Base
 
-def digits(n: Nat, acc: String) -> String:
+def digits(n: Nat, +digit: Char, acc: String) -> String:
   match n:
     case 0n:
       acc
     case 1n+p:
-      digits(p, SCon{'1', acc})
+      digits(p, digit, SCon{digit, acc})
 
 def seen(m: Maybe<&2, F32>) -> String:
   match m:
@@ -18,6 +19,10 @@ def seen(m: Maybe<&2, F32>) -> String:
       F32.show(v)
 
 def main() -> IO(Unit):
-  IO.print(seen(F32.read(digits(100000n, "x"))))
+  do IO<Unit>:
+    IO.print(seen(F32.read(digits(100000n, '1', "x"))))
+    IO.print(seen(F32.read("1.000000059604644775390625"
+      ++ digits(5000n, '0', " "))))
 
 #|none
+#|none