diff --git a/extlib/benz/number.c b/extlib/benz/number.c
index 3f9c3aa0..90b47f7e 100644
--- a/extlib/benz/number.c
+++ b/extlib/benz/number.c
@@ -216,12 +216,19 @@ pic_number_string_to_number(pic_state *pic)
       : pic_float_value(num);
   }
 
-  flo = pic_read_cstr(pic, str);
+  pic_try {
+    flo = pic_read_cstr(pic, str);
+  }
+  pic_catch {
+    // swallow error
+    flo = pic_false_value();
+  }
+
   if (pic_int_p(flo) || pic_float_p(flo)) {
     return flo;
   }
 
-  pic_errorf(pic, "invalid string given: %s", str);
+  return pic_false_value();
 }
 
 void
diff --git a/extlib/benz/read.c b/extlib/benz/read.c
index eeca5485..b4bd1f4e 100644
--- a/extlib/benz/read.c
+++ b/extlib/benz/read.c
@@ -283,6 +283,10 @@ read_unsigned(pic_state *pic, struct pic_port *port, int c)
   if (idx >= ATOF_BUF_SIZE)
     read_error(pic, "number too large", 
                     pic_obj_value(pic_make_str(pic, (const char *)buf, ATOF_BUF_SIZE)));
+
+  if (! isdelim(c))
+    read_error(pic, "non-delimiter character given after number", pic_list1(pic, pic_char_value(c)));
+
   buf[idx] = 0;
   flt = PIC_CSTRING_TO_DOUBLE(buf);
 
diff --git a/t/issue/322.scm b/t/issue/322.scm
new file mode 100644
index 00000000..59bba7cc
--- /dev/null
+++ b/t/issue/322.scm
@@ -0,0 +1,26 @@
+(import (scheme base)
+        (picrin test))
+
+(test-begin)
+
+(test #f (string->number "12e43r"))
+
+(test #f (string->number "12e+43r"))
+
+(test #f (string->number "12e+43e54"))
+
+(test #f (string->number "12e+"))
+
+(test #f (string->number "12e"))
+
+(test #f (string->number "+12e"))
+
+(test #f (string->number "-12e"))
+
+(test -12 (string->number "-12"))
+
+(test -12.0 (string->number "-12.0"))
+
+(test #f (string->number "-12.0e-5t"))
+
+(test-end)