diff --git a/ext/bigdecimal/bigdecimal.c b/ext/bigdecimal/bigdecimal.c
index 4d16590b..fcc29a08 100644
--- a/ext/bigdecimal/bigdecimal.c
+++ b/ext/bigdecimal/bigdecimal.c
@@ -293,8 +293,9 @@ GetVpValueWithPrec(VALUE v, long prec, int must)
 
 #ifdef ENABLE_NUMERIC_STRING
       case T_STRING:
-	SafeStringValue(v);
-	return VpCreateRbObject(strlen(RSTRING_PTR(v)) + VpBaseFig() + 1,
+	StringValueCStr(v);
+	rb_check_safe_obj(v);
+	return VpCreateRbObject(RSTRING_LEN(v) + VpBaseFig() + 1,
 				RSTRING_PTR(v));
 #endif /* ENABLE_NUMERIC_STRING */
 
@@ -434,8 +435,8 @@ BigDecimal_load(VALUE self, VALUE str)
     unsigned char ch;
     unsigned long m=0;
 
-    SafeStringValue(str);
-    pch = (unsigned char *)RSTRING_PTR(str);
+    pch = (unsigned char *)StringValueCStr(str);
+    rb_check_safe_obj(str);
     /* First get max prec */
     while((*pch) != (unsigned char)'\0' && (ch = *pch++) != (unsigned char)':') {
         if(!ISDIGIT(ch)) {
@@ -2042,8 +2043,8 @@ BigDecimal_to_s(int argc, VALUE *argv, VALUE self)
 
     if (rb_scan_args(argc, argv, "01", &f) == 1) {
 	if (RB_TYPE_P(f, T_STRING)) {
-	    SafeStringValue(f);
-	    psz = RSTRING_PTR(f);
+	    psz = StringValueCStr(f);
+	    rb_check_safe_obj(f);
 	    if (*psz == ' ') {
 		fPlus = 1;
 		psz++;