diff --git a/rational.c b/rational.c
index c5ad7598f7d592..3b82016f323087 100644
--- a/rational.c
+++ b/rational.c
@@ -389,8 +389,8 @@ f_gcd(VALUE x, VALUE y)
 {
     VALUE r = f_gcd_orig(x, y);
     if (f_nonzero_p(r)) {
-        assert(f_zero_p(f_mod(x, r)));
-        assert(f_zero_p(f_mod(y, r)));
+        RUBY_ASSERT(f_zero_p(f_mod(x, r)));
+        RUBY_ASSERT(f_zero_p(f_mod(y, r)));
     }
     return r;
 }
@@ -456,8 +456,8 @@ nurat_int_value(VALUE num)
 static void
 nurat_canonicalize(VALUE *num, VALUE *den)
 {
-    assert(num); assert(RB_INTEGER_TYPE_P(*num));
-    assert(den); assert(RB_INTEGER_TYPE_P(*den));
+    RUBY_ASSERT(num); RUBY_ASSERT(RB_INTEGER_TYPE_P(*num));
+    RUBY_ASSERT(den); RUBY_ASSERT(RB_INTEGER_TYPE_P(*den));
     if (INT_NEGATIVE_P(*den)) {
         *num = rb_int_uminus(*num);
         *den = rb_int_uminus(*den);
@@ -497,16 +497,16 @@ nurat_s_canonicalize_internal_no_reduce(VALUE klass, VALUE num, VALUE den)
 inline static VALUE
 f_rational_new2(VALUE klass, VALUE x, VALUE y)
 {
-    assert(!k_rational_p(x));
-    assert(!k_rational_p(y));
+    RUBY_ASSERT(!k_rational_p(x));
+    RUBY_ASSERT(!k_rational_p(y));
     return nurat_s_canonicalize_internal(klass, x, y);
 }
 
 inline static VALUE
 f_rational_new_no_reduce2(VALUE klass, VALUE x, VALUE y)
 {
-    assert(!k_rational_p(x));
-    assert(!k_rational_p(y));
+    RUBY_ASSERT(!k_rational_p(x));
+    RUBY_ASSERT(!k_rational_p(y));
     return nurat_s_canonicalize_internal_no_reduce(klass, x, y);
 }
 
@@ -610,7 +610,7 @@ nurat_denominator(VALUE self)
 VALUE
 rb_rational_uminus(VALUE self)
 {
-    const int unused = (assert(RB_TYPE_P(self, T_RATIONAL)), 0);
+    const int unused = (RUBY_ASSERT(RB_TYPE_P(self, T_RATIONAL)), 0);
     get_dat1(self);
     (void)unused;
     return f_rational_new2(CLASS_OF(self), rb_int_uminus(dat->num), dat->den);
@@ -646,7 +646,7 @@ inline static VALUE
 f_imul(long x, long y)
 {
     VALUE r = f_imul_orig(x, y);
-    assert(f_eqeq_p(r, f_mul(LONG2NUM(x), LONG2NUM(y))));
+    RUBY_ASSERT(f_eqeq_p(r, f_mul(LONG2NUM(x), LONG2NUM(y))));
     return r;
 }
 #endif
@@ -795,7 +795,7 @@ f_muldiv(VALUE self, VALUE anum, VALUE aden, VALUE bnum, VALUE bden, int k)
 {
     VALUE num, den;
 
-    assert(RB_TYPE_P(self, T_RATIONAL));
+    RUBY_ASSERT(RB_TYPE_P(self, T_RATIONAL));
 
     /* Integer#** can return Rational with Float right now */
     if (RB_FLOAT_TYPE_P(anum) || RB_FLOAT_TYPE_P(aden) ||
@@ -806,10 +806,10 @@ f_muldiv(VALUE self, VALUE anum, VALUE aden, VALUE bnum, VALUE bden, int k)
         return DBL2NUM(x);
     }
 
-    assert(RB_INTEGER_TYPE_P(anum));
-    assert(RB_INTEGER_TYPE_P(aden));
-    assert(RB_INTEGER_TYPE_P(bnum));
-    assert(RB_INTEGER_TYPE_P(bden));
+    RUBY_ASSERT(RB_INTEGER_TYPE_P(anum));
+    RUBY_ASSERT(RB_INTEGER_TYPE_P(aden));
+    RUBY_ASSERT(RB_INTEGER_TYPE_P(bnum));
+    RUBY_ASSERT(RB_INTEGER_TYPE_P(bden));
 
     if (k == '/') {
         VALUE t;
@@ -2559,7 +2559,7 @@ nurat_convert(VALUE klass, VALUE numv, VALUE denv, int raise)
     VALUE a1 = numv, a2 = denv;
     int state;
 
-    assert(!UNDEF_P(a1));
+    RUBY_ASSERT(!UNDEF_P(a1));
 
     if (NIL_P(a1) || NIL_P(a2)) {
         if (!raise) return Qnil;