diff --git a/src/regexp/onepass.go b/src/regexp/onepass.go
index 1f8c1d00bd..4440419225 100644
--- a/src/regexp/onepass.go
+++ b/src/regexp/onepass.go
@@ -350,17 +350,17 @@ func makeOnePass(p *onePassProg) *onePassProg {
 			m[pc] = m[inst.Out]
 			// pass matching runes back through these no-ops.
 			onePassRunes[pc] = append([]rune{}, onePassRunes[inst.Out]...)
-			inst.Next = []uint32{}
-			for i := len(onePassRunes[pc]) / 2; i >= 0; i-- {
-				inst.Next = append(inst.Next, inst.Out)
+			inst.Next = make([]uint32, len(onePassRunes[pc])/2+1)
+			for i := range inst.Next {
+				inst.Next[i] = inst.Out
 			}
 		case syntax.InstEmptyWidth:
 			ok = check(inst.Out, m)
 			m[pc] = m[inst.Out]
 			onePassRunes[pc] = append([]rune{}, onePassRunes[inst.Out]...)
-			inst.Next = []uint32{}
-			for i := len(onePassRunes[pc]) / 2; i >= 0; i-- {
-				inst.Next = append(inst.Next, inst.Out)
+			inst.Next = make([]uint32, len(onePassRunes[pc])/2+1)
+			for i := range inst.Next {
+				inst.Next[i] = inst.Out
 			}
 		case syntax.InstMatch, syntax.InstFail:
 			m[pc] = inst.Op == syntax.InstMatch
@@ -388,9 +388,9 @@ func makeOnePass(p *onePassProg) *onePassProg {
 				runes = append(runes, inst.Rune...)
 			}
 			onePassRunes[pc] = runes
-			inst.Next = []uint32{}
-			for i := len(onePassRunes[pc]) / 2; i >= 0; i-- {
-				inst.Next = append(inst.Next, inst.Out)
+			inst.Next = make([]uint32, len(onePassRunes[pc])/2+1)
+			for i := range inst.Next {
+				inst.Next[i] = inst.Out
 			}
 			inst.Op = syntax.InstRune
 		case syntax.InstRune1:
@@ -412,9 +412,9 @@ func makeOnePass(p *onePassProg) *onePassProg {
 				runes = append(runes, inst.Rune[0], inst.Rune[0])
 			}
 			onePassRunes[pc] = runes
-			inst.Next = []uint32{}
-			for i := len(onePassRunes[pc]) / 2; i >= 0; i-- {
-				inst.Next = append(inst.Next, inst.Out)
+			inst.Next = make([]uint32, len(onePassRunes[pc])/2+1)
+			for i := range inst.Next {
+				inst.Next[i] = inst.Out
 			}
 			inst.Op = syntax.InstRune
 		case syntax.InstRuneAny:
@@ -432,9 +432,9 @@ func makeOnePass(p *onePassProg) *onePassProg {
 			}
 			instQueue.insert(inst.Out)
 			onePassRunes[pc] = append([]rune{}, anyRuneNotNL...)
-			inst.Next = []uint32{}
-			for i := len(onePassRunes[pc]) / 2; i >= 0; i-- {
-				inst.Next = append(inst.Next, inst.Out)
+			inst.Next = make([]uint32, len(onePassRunes[pc])/2+1)
+			for i := range inst.Next {
+				inst.Next[i] = inst.Out
 			}
 		}
 		return