diff --git a/internal/impl/validate.go b/internal/impl/validate.go
index 40c6a7a..bb6d47d 100644
--- a/internal/impl/validate.go
+++ b/internal/impl/validate.go
@@ -249,7 +249,6 @@
 				return ValidationUnknown
 			}
 		}
-	Field:
 		for len(b) > 0 {
 			// Parse the tag (field number and wire type).
 			var tag uint64
@@ -358,100 +357,152 @@
 					st.requiredMask |= vi.requiredBit
 				}
 			}
-			switch vi.typ {
-			case validationTypeMessage, validationTypeMap:
-				if wtyp != wire.BytesType {
-					break
+
+			switch wtyp {
+			case wire.VarintType:
+				if len(b) >= 10 {
+					switch {
+					case b[0] < 0x80:
+						b = b[1:]
+					case b[1] < 0x80:
+						b = b[2:]
+					case b[2] < 0x80:
+						b = b[3:]
+					case b[3] < 0x80:
+						b = b[4:]
+					case b[4] < 0x80:
+						b = b[5:]
+					case b[5] < 0x80:
+						b = b[6:]
+					case b[6] < 0x80:
+						b = b[7:]
+					case b[7] < 0x80:
+						b = b[8:]
+					case b[8] < 0x80:
+						b = b[9:]
+					case b[9] < 0x80:
+						b = b[10:]
+					default:
+						return ValidationInvalid
+					}
+				} else {
+					switch {
+					case len(b) > 0 && b[0] < 0x80:
+						b = b[1:]
+					case len(b) > 1 && b[1] < 0x80:
+						b = b[2:]
+					case len(b) > 2 && b[2] < 0x80:
+						b = b[3:]
+					case len(b) > 3 && b[3] < 0x80:
+						b = b[4:]
+					case len(b) > 4 && b[4] < 0x80:
+						b = b[5:]
+					case len(b) > 5 && b[5] < 0x80:
+						b = b[6:]
+					case len(b) > 6 && b[6] < 0x80:
+						b = b[7:]
+					case len(b) > 7 && b[7] < 0x80:
+						b = b[8:]
+					case len(b) > 8 && b[8] < 0x80:
+						b = b[9:]
+					case len(b) > 9 && b[9] < 0x80:
+						b = b[10:]
+					default:
+						return ValidationInvalid
+					}
 				}
-				if vi.mi == nil && vi.typ == validationTypeMessage {
-					return ValidationUnknown
-				}
-				size, n := wire.ConsumeVarint(b)
-				if n < 0 {
-					return ValidationInvalid
-				}
-				b = b[n:]
-				if uint64(len(b)) < size {
-					return ValidationInvalid
-				}
-				states = append(states, validationState{
-					typ:     vi.typ,
-					keyType: vi.keyType,
-					valType: vi.valType,
-					mi:      vi.mi,
-					tail:    b[size:],
-				})
-				b = b[:size]
 				continue State
-			case validationTypeGroup:
-				if wtyp != wire.StartGroupType {
-					break
-				}
-				if vi.mi == nil {
-					return ValidationUnknown
-				}
-				states = append(states, validationState{
-					typ:      validationTypeGroup,
-					mi:       vi.mi,
-					endGroup: num,
-				})
-				continue State
-			case validationTypeRepeatedVarint:
-				if wtyp != wire.BytesType {
-					break
-				}
-				// Packed field.
-				v, n := wire.ConsumeBytes(b)
-				if n < 0 {
-					return ValidationInvalid
-				}
-				b = b[n:]
-				for len(v) > 0 {
-					_, n := wire.ConsumeVarint(v)
+			case wire.BytesType:
+				var size uint64
+				if b[0] < 0x80 {
+					size = uint64(b[0])
+					b = b[1:]
+				} else if len(b) >= 2 && b[1] < 128 {
+					size = uint64(b[0]&0x7f) + uint64(b[1])<<7
+					b = b[2:]
+				} else {
+					var n int
+					size, n = wire.ConsumeVarint(b)
 					if n < 0 {
 						return ValidationInvalid
 					}
-					v = v[n:]
+					b = b[n:]
 				}
-				continue Field
-			case validationTypeRepeatedFixed32:
-				if wtyp != wire.BytesType {
-					break
-				}
-				// Packed field.
-				v, n := wire.ConsumeBytes(b)
-				if n < 0 || len(v)%4 != 0 {
+				if size > uint64(len(b)) {
 					return ValidationInvalid
 				}
-				b = b[n:]
-				continue Field
-			case validationTypeRepeatedFixed64:
-				if wtyp != wire.BytesType {
-					break
+				v := b[:size]
+				b = b[size:]
+				switch vi.typ {
+				case validationTypeMessage, validationTypeMap:
+					if vi.mi == nil && vi.typ == validationTypeMessage {
+						return ValidationUnknown
+					}
+					states = append(states, validationState{
+						typ:     vi.typ,
+						keyType: vi.keyType,
+						valType: vi.valType,
+						mi:      vi.mi,
+						tail:    b,
+					})
+					b = v
+					continue State
+				case validationTypeRepeatedVarint:
+					// Packed field.
+					for len(v) > 0 {
+						_, n := wire.ConsumeVarint(v)
+						if n < 0 {
+							return ValidationInvalid
+						}
+						v = v[n:]
+					}
+				case validationTypeRepeatedFixed32:
+					// Packed field.
+					if len(v)%4 != 0 {
+						return ValidationInvalid
+					}
+				case validationTypeRepeatedFixed64:
+					// Packed field.
+					if len(v)%8 != 0 {
+						return ValidationInvalid
+					}
+				case validationTypeUTF8String:
+					if !utf8.Valid(v) {
+						return ValidationInvalid
+					}
 				}
-				// Packed field.
-				v, n := wire.ConsumeBytes(b)
-				if n < 0 || len(v)%8 != 0 {
+			case wire.Fixed32Type:
+				if len(b) < 4 {
 					return ValidationInvalid
 				}
-				b = b[n:]
-				continue Field
-			case validationTypeUTF8String:
-				if wtyp != wire.BytesType {
-					break
-				}
-				v, n := wire.ConsumeBytes(b)
-				if n < 0 || !utf8.Valid(v) {
+				b = b[4:]
+			case wire.Fixed64Type:
+				if len(b) < 8 {
 					return ValidationInvalid
 				}
-				b = b[n:]
-				continue Field
-			}
-			n := wire.ConsumeFieldValue(num, wtyp, b)
-			if n < 0 {
+				b = b[8:]
+			case wire.StartGroupType:
+				switch vi.typ {
+				case validationTypeGroup:
+					if vi.mi == nil {
+						return ValidationUnknown
+					}
+					states = append(states, validationState{
+						typ:      validationTypeGroup,
+						mi:       vi.mi,
+						endGroup: num,
+					})
+					continue State
+				default:
+					n := wire.ConsumeFieldValue(num, wtyp, b)
+					if n < 0 {
+						return ValidationInvalid
+					}
+					b = b[n:]
+				}
+			default:
 				return ValidationInvalid
 			}
-			b = b[n:]
 		}
 		if st.endGroup != 0 {
 			return ValidationInvalid