diff --git a/encoding/prototext/decode_test.go b/encoding/prototext/decode_test.go
index 3597d9b6f..2f8b59607 100644
--- a/encoding/prototext/decode_test.go
+++ b/encoding/prototext/decode_test.go
@@ -308,6 +308,11 @@ s_string: "谷歌"
 		inputMessage: &pb3.Scalars{},
 		inputText:    "s_sfixed64: bad",
 		wantErr:      "invalid value for sfixed64",
+	}, {
+		desc:         "incomplete number value",
+		inputMessage: &pb3.Scalars{},
+		inputText:    `s_int32: - `,
+		wantErr:      "(line 1:10): invalid scalar value: -",
 	}, {
 		desc:         "conformance: FloatFieldMaxValue",
 		inputMessage: &pb2.Scalars{},
diff --git a/internal/encoding/text/decode_number.go b/internal/encoding/text/decode_number.go
index 3dc8e9787..45c81f029 100644
--- a/internal/encoding/text/decode_number.go
+++ b/internal/encoding/text/decode_number.go
@@ -88,15 +88,15 @@ func parseNumber(input []byte) number {
 		neg = true
 		s = s[1:]
 		size++
-		if len(s) == 0 {
-			return number{}
-		}
 		// Consume any whitespace or comments between the
 		// negative sign and the rest of the number
 		lenBefore := len(s)
 		s = consume(s, 0)
 		sep = lenBefore - len(s)
 		size += sep
+		if len(s) == 0 {
+			return number{}
+		}
 	}
 
 	switch {
diff --git a/internal/encoding/text/decode_test.go b/internal/encoding/text/decode_test.go
index 528b1bc71..7c705ab51 100644
--- a/internal/encoding/text/decode_test.go
+++ b/internal/encoding/text/decode_test.go
@@ -559,6 +559,14 @@ func TestDecoder(t *testing.T) {
 			in:   "- \t 123.321e6",
 			want: []R{{E: "invalid field number: -123.321e6"}},
 		},
+		{
+			in:   "-",
+			want: []R{{E: "invalid field name: -"}},
+		},
+		{
+			in:   "- ",
+			want: []R{{E: "invalid field name: -"}},
+		},
 		{
 			in:   "- # negative\n 123",
 			want: []R{{E: "invalid field number: -123"}},