diff --git a/src/c/num_pred.d b/src/c/num_pred.d
index 1ca72747d..edb51e6b2 100644
--- a/src/c/num_pred.d
+++ b/src/c/num_pred.d
@@ -64,17 +64,16 @@ si_float_infinity_p(cl_object x)
 bool
 ecl_float_nan_p(cl_object x)
 {
-  return !ecl_number_equalp(x,x);
-/*   switch (ecl_t_of(x)) { */
-/*   case t_singlefloat: */
-/*     return !isnan(ecl_single_float(x)); */
-/*   case t_doublefloat: */
-/*     return !isnan(ecl_double_float(x)); */
-/*   case t_longfloat: */
-/*     return !isnan(ecl_long_float(x)); */
-/*   default: */
-/*     return 0; */
-/*   } */
+  switch (ecl_t_of(x)) {
+  case t_singlefloat:
+    return isnan(ecl_single_float(x));
+  case t_doublefloat:
+    return isnan(ecl_double_float(x));
+  case t_longfloat:
+    return isnan(ecl_long_float(x));
+  default:
+    return 0;
+  }
 }
 
 bool
@@ -82,11 +81,11 @@ ecl_float_infinity_p(cl_object x)
 {
   switch (ecl_t_of(x)) {
   case t_singlefloat:
-    return !isfinite(ecl_single_float(x));
+    return isinf(ecl_single_float(x));
   case t_doublefloat:
-    return !isfinite(ecl_double_float(x));
+    return isinf(ecl_double_float(x));
   case t_longfloat:
-    return !isfinite(ecl_long_float(x));
+    return isinf(ecl_long_float(x));
   default:
     return 0;
   }