diff --git a/ext/gsl_native/dht.c b/ext/gsl_native/dht.c
index 618eb35..ffaa54f 100644
--- a/ext/gsl_native/dht.c
+++ b/ext/gsl_native/dht.c
@@ -148,7 +148,7 @@ static VALUE rb_gsl_dht_xk_sample(VALUE obj, VALUE n,
       }
       return ary;
 #endif
-#ifdef HAVE_NARRAY_H
+#ifdef HAVE_NMATRIX_H
     } else if (NM_IsNMatrix(n)) {
       NM_DENSE_STORAGE *nm;
       int *ptr;
diff --git a/ext/gsl_native/spline.c b/ext/gsl_native/spline.c
index 0d730da..37565ba 100644
--- a/ext/gsl_native/spline.c
+++ b/ext/gsl_native/spline.c
@@ -85,7 +85,7 @@ static VALUE rb_gsl_spline_init(VALUE obj, VALUE xxa, VALUE yya)
     size = nax->total;
     ptr1 = (double *) nax->ptr;
 #endif
-#ifdef HAVE_NARRAY_H
+#ifdef HAVE_NMATRIX_H
   } else if (NM_IsNMatrix(xxa)) {
     NM_DENSE_STORAGE *nmx = NULL;
     nmx = NM_STORAGE_DENSE(xxa);
@@ -108,7 +108,7 @@ static VALUE rb_gsl_spline_init(VALUE obj, VALUE xxa, VALUE yya)
     ptr2 = (double *) nay->ptr;
 #endif
 
-#ifdef HAVE_NARRAY_H
+#ifdef HAVE_NMATRIX_H
   } else if (NM_IsNMatrix(yya)) {
     NM_DENSE_STORAGE *nmy;
     nmy = NM_STORAGE_DENSE(yya);