diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7f270f22..4ec00b84 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -17,6 +17,7 @@ Bug Fixes
 - Fix `read-line` to read entire lines that consist of more than 1022 bytes. Previously the function would only return partial data up to this limit. Thanks to Robby Zambito for the bug report.
 - `(include "body.scm")` inside a file `path/to/lib.sld` will look for `path/to/body.scm`, then fallback to the legacy behavior, and look for `$(pwd)/body.scm`.
 - Pass append and prepend directories when compiling dependent libraries of a program. This prevents issues where the directories are not made available to any `include` directives within such libraries.
+- Updated the reader to throw an error if a number cannot be parsed, rather than returning `#f`.
 
 ## 0.35.0 - August 25, 2022
 
diff --git a/scheme/read.sld b/scheme/read.sld
index efc41e21..0b67f6e4 100644
--- a/scheme/read.sld
+++ b/scheme/read.sld
@@ -179,6 +179,12 @@
   "(void *data, object ptr, object opq)"
   " return(Cyc_is_string(opaque_ptr(opq)));")
 
+(define-c Cyc-opaque->string
+  "(void *data, int argc, closure _, object k, object opq)"
+  " return_closcall1(data, k, opaque_ptr(opq));"
+  "(void *data, object ptr, object opq)"
+  " return(opaque_ptr(opq));")
+
 (define-c Cyc-opaque-unsafe-string->number
   "(void *data, int argc, closure _, object k, object opq)"
   " Cyc_string2number_(data, k, opaque_ptr(opq));")
@@ -226,7 +232,10 @@
       ((Cyc-opaque? token)
        (cond
          ((Cyc-opaque-unsafe-string? token)
-          (Cyc-opaque-unsafe-string->number token))
+          (let ((rv (Cyc-opaque-unsafe-string->number token)))
+            (if rv
+                rv
+                (error "Invalid numeric syntax" (Cyc-opaque->string token)))))
          ;; Open paren, start read loop
          ((Cyc-opaque-unsafe-eq? token #\()
           (let ((line-num (get-line-num fp))