diff --git a/collects/tests/racket/numstrs.rktl b/collects/tests/racket/numstrs.rktl
index 99e7df8126..9eead56d6b 100644
--- a/collects/tests/racket/numstrs.rktl
+++ b/collects/tests/racket/numstrs.rktl
@@ -43,6 +43,8 @@
     (-0.0 "-1e-10000000000000000000000000000000")
     (+0.0 "1#e-10000000000000000000000000000000")
     (-0.0 "-1#e-10000000000000000000000000000000")
+    (1e-134
+     "0.00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001")
     (10.0 "1#")
     (10.0 "1#e0")
     (10.0 "1####e-3")
diff --git a/src/racket/src/numstr.c b/src/racket/src/numstr.c
index 3a1ab46cd2..ad6536d497 100644
--- a/src/racket/src/numstr.c
+++ b/src/racket/src/numstr.c
@@ -245,15 +245,15 @@ static Scheme_Object *read_special_number(const mzchar *str, int pos)
   return NULL;
 }
 
-/* Don't bother reading more than the following number of digits in a
-   floating-point mantissa: */
-#define MAX_FLOATREAD_PRECISION_DIGITS 50
-
 /* Exponent threshold for obvious infinity. Must be at least
    max(MAX_FAST_FLOATREAD_LEN, MAX_FLOATREAD_PRECISION_DIGITS) more
    than the larget possible FP exponent. */
 #define CHECK_INF_EXP_THRESHOLD 400
 
+/* Don't bother reading more than the following number of digits in a
+   floating-point mantissa: */
+#define MAX_FLOATREAD_PRECISION_DIGITS CHECK_INF_EXP_THRESHOLD
+
 #ifdef USE_EXPLICT_FP_FORM_CHECK
 
 /* Fixes Linux problem of 0e...  => non-number (0 with ptr at e...) */