diff --git a/numeric.c b/numeric.c
index 99a1c7d60e..88fff399c7 100644
--- a/numeric.c
+++ b/numeric.c
@@ -1805,26 +1805,22 @@ VALUE
 ruby_num_interval_step_size(VALUE from, VALUE to, VALUE step, int excl)
 {
     if (FIXNUM_P(from) && FIXNUM_P(to) && FIXNUM_P(step)) {
-	long delta, diff, result;
+	long delta, diff;
 
 	diff = FIX2LONG(step);
 	if (!diff) rb_num_zerodiv();
 	delta = FIX2LONG(to) - FIX2LONG(from);
+	if (diff < 0) {
+	    diff = -diff;
+	    delta = -delta;
+	}
 	if (excl) {
-	    delta += (diff > 0 ? -1 : +1);
+	    delta--;
 	}
-	if (delta) {
-	    if (diff < 0) {
-		if (delta > 0) return INT2FIX(0);
-		diff = -diff;
-		delta = -delta;
-	    }
-	    else {
-		if (delta < 0) return INT2FIX(0);
-	    }
+	if (delta < 0) {
+	    return INT2FIX(0);
 	}
-	result = delta / diff;
-	return LONG2FIX(result >= 0 ? result + 1 : 0);
+	return LONG2FIX(delta / diff + 1);
     }
     else if (RB_TYPE_P(from, T_FLOAT) || RB_TYPE_P(to, T_FLOAT) || RB_TYPE_P(step, T_FLOAT)) {
 	double n = ruby_float_step_size(NUM2DBL(from), NUM2DBL(to), NUM2DBL(step), excl);