diff --git a/libguile/numbers.c b/libguile/numbers.c
index ff7ce2821..769562829 100644
--- a/libguile/numbers.c
+++ b/libguile/numbers.c
@@ -2450,7 +2450,11 @@ scm_string_to_number (str, radix)
   if (SCM_UNBNDP (radix))
     radix = SCM_MAKINUM (10L);
   else
-    SCM_ASSERT (SCM_INUMP (radix), radix, SCM_ARG2, s_string_to_number);
+    {
+      SCM_ASSERT (SCM_INUMP (radix), radix, SCM_ARG2, s_string_to_number);
+      SCM_ASSERT (SCM_INUM (radix) >= 2, radix, SCM_OUTOFRANGE,
+		  s_number_to_string);
+    }
   SCM_ASSERT (SCM_NIMP (str) && SCM_ROSTRINGP (str),
 	      str, SCM_ARG1, s_string_to_number);
   answer = scm_istring2number (SCM_ROCHARS (str),
diff --git a/libguile/print.c b/libguile/print.c
index 9fe3c0b96..31936f1e9 100644
--- a/libguile/print.c
+++ b/libguile/print.c
@@ -917,8 +917,8 @@ scm_write (obj, port)
 {
   if (SCM_UNBNDP (port))
     port = scm_cur_outp;
-  else
-    SCM_ASSERT (scm_valid_oport_value_p (port), port, SCM_ARG2, s_write);
+
+  SCM_ASSERT (scm_valid_oport_value_p (port), port, SCM_ARG2, s_write);
 
   scm_prin1 (obj, port, 1);
 #ifdef HAVE_PIPE
@@ -940,8 +940,8 @@ scm_display (obj, port)
 {
   if (SCM_UNBNDP (port))
     port = scm_cur_outp;
-  else
-    SCM_ASSERT (scm_valid_oport_value_p (port), port, SCM_ARG2, s_display);
+
+  SCM_ASSERT (scm_valid_oport_value_p (port), port, SCM_ARG2, s_display);
 
   scm_prin1 (obj, port, 0);
 #ifdef HAVE_PIPE
@@ -961,8 +961,8 @@ scm_newline (port)
 {
   if (SCM_UNBNDP (port))
     port = scm_cur_outp;
-  else
-    SCM_ASSERT (scm_valid_oport_value_p (port), port, SCM_ARG1, s_newline);
+
+  SCM_ASSERT (scm_valid_oport_value_p (port), port, SCM_ARG1, s_newline);
 
   scm_putc ('\n', SCM_COERCE_OUTPORT (port));
   return SCM_UNSPECIFIED;
@@ -977,8 +977,8 @@ scm_write_char (chr, port)
 {
   if (SCM_UNBNDP (port))
     port = scm_cur_outp;
-  else
-    SCM_ASSERT (scm_valid_oport_value_p (port), port, SCM_ARG2, s_write_char);
+
+  SCM_ASSERT (scm_valid_oport_value_p (port), port, SCM_ARG2, s_write_char);
 
   SCM_ASSERT (SCM_ICHRP (chr), chr, SCM_ARG1, s_write_char);
   scm_putc ((int) SCM_ICHR (chr), SCM_COERCE_OUTPORT (port));