diff --git a/src/racket/src/number.c b/src/racket/src/number.c
index a1692629e4..c49e0e0f9d 100644
--- a/src/racket/src/number.c
+++ b/src/racket/src/number.c
@@ -2039,9 +2039,12 @@ real_to_double_flonum (int argc, Scheme_Object *argv[])
 static Scheme_Object *
 real_to_long_double_flonum (int argc, Scheme_Object *argv[])
 {
-  CHECK_MZ_LONG_DOUBLE_UNSUPPORTED("real->extfl");
 #ifdef MZ_LONG_DOUBLE
+  CHECK_MZ_LONG_DOUBLE_UNSUPPORTED("real->extfl");
   return scheme_TO_LONG_DOUBLE(argv[0]);
+#else
+  scheme_raise_exn(MZEXN_FAIL_UNSUPPORTED, "real->extfl" ": " NOT_SUPPORTED_STR);
+  ESCAPED_BEFORE_HERE;
 #endif
 }
 
@@ -4015,7 +4018,8 @@ extfl_to_exact (int argc, Scheme_Object *argv[])
   
   return scheme_rational_from_long_double(d);
 #else
-  CHECK_MZ_LONG_DOUBLE_UNSUPPORTED("extfl->exact");
+  scheme_raise_exn(MZEXN_FAIL_UNSUPPORTED, "extfl->exact" ": " NOT_SUPPORTED_STR);
+  ESCAPED_BEFORE_HERE;
 #endif
 }
 
diff --git a/src/racket/src/numstr.c b/src/racket/src/numstr.c
index 2484933329..d1596a1d19 100644
--- a/src/racket/src/numstr.c
+++ b/src/racket/src/numstr.c
@@ -1925,6 +1925,7 @@ static char *number_to_allocated_string(int radix, Scheme_Object *obj, int alloc
                             "number", 1, obj,
                             "requested base", 1, scheme_make_integer(radix),
                             NULL);
+    memset(&stub, 0, sizeof(long_double));
     s = double_to_string(SCHEME_FLOAT_VAL(obj), alloc, SCHEME_FLTP(obj), 0, stub);
   } else if (SCHEME_LONG_DBLP(obj)) {
     if (radix != 10)