diff --git a/promql/fuzz.go b/promql/fuzz.go
index 796fe4491..3d3864fdf 100644
--- a/promql/fuzz.go
+++ b/promql/fuzz.go
@@ -1,67 +1,91 @@
-package promql
+// Copyright 2015 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Only build when go-fuzz is in use
 // +build gofuzz
 
-/* PromQL parser fuzzing instrumentation for use with https://github.com/dvyukov/go-fuzz.
- * 
- * Fuzz each parser by building appropriately instrumented parser, ex. FuzzParseMetric and execute it with it's 
- *
- *     go-fuzz-build -func FuzzParseMetric -o FuzzParseMetric.zip github.com/prometheus/prometheus/promql
- *
- * And then run the tests with the appropriate inputs
- *
- *     go-fuzz -bin FuzzParseMetric.zip -workdir fuzz-data/ParseMetric
- *
- * Further input samples should go in the folders fuzz-data/ParseMetric/corpus.
- *
- * Repeat for ParseMetricSeletion, ParseExpr and ParseStmt
- */
+package promql
 
+// PromQL parser fuzzing instrumentation for use with
+// https://github.com/dvyukov/go-fuzz.
+//
+// Fuzz each parser by building appropriately instrumented parser, ex.
+// FuzzParseMetric and execute it with it's
+//
+//     go-fuzz-build -func FuzzParseMetric -o FuzzParseMetric.zip github.com/prometheus/prometheus/promql
+//
+// And then run the tests with the appropriate inputs
+//
+//     go-fuzz -bin FuzzParseMetric.zip -workdir fuzz-data/ParseMetric
+//
+// Further input samples should go in the folders fuzz-data/ParseMetric/corpus.
+//
+// Repeat for ParseMetricSeletion, ParseExpr and ParseStmt.
+
+// Tuning which value is returned from Fuzz*-functions has a strong influence
+// on how quick the fuzzer converges on "interesting" cases. At least try
+// switching between fuzzMeh (= included in corpus, but not a priority) and
+// fuzzDiscard (=don't use this input for re-building later inputs) when
+// experimenting.
 const (
-	fuzz_interesting = 1
-	fuzz_meh         = 0
-	fuzz_discard     = -1
+	fuzzInteresting = 1
+	fuzzMeh         = 0
+	fuzzDiscard     = -1
 )
 
-// Fuzz the metric parser
+// Fuzz the metric parser.
+//
+// Note that his is not the parser for the text-based exposition-format; that
+// lives in github.com/prometheus/client_golang/text.
 func FuzzParseMetric(in []byte) int {
-    _, err := ParseMetric(string(in))
+	_, err := ParseMetric(string(in))
 
-    if err == nil {
-        return fuzz_interesting
-    }
+	if err == nil {
+		return fuzzInteresting
+	}
 
-    return fuzz_discard
+	return fuzzDiscard
 }
 
-// Fuzz the metric selector parser
+// Fuzz the metric selector parser.
 func FuzzParseMetricSelector(in []byte) int {
-    _, err := ParseMetricSelector(string(in))
+	_, err := ParseMetricSelector(string(in))
 
-    if err == nil {
-        return fuzz_interesting
-    }
+	if err == nil {
+		return fuzzInteresting
+	}
 
-    return fuzz_discard
+	return fuzzDiscard
 }
 
-// Fuzz the expression parser
+// Fuzz the expression parser.
 func FuzzParseExpr(in []byte) int {
-    _, err := ParseExpr(string(in))
+	_, err := ParseExpr(string(in))
 
-    if err == nil {
-        return fuzz_interesting
-    }
+	if err == nil {
+		return fuzzInteresting
+	}
 
-    return fuzz_discard
+	return fuzzDiscard
 }
 
-// Fuzz the  parser
+// Fuzz the parser.
 func FuzzParseStmts(in []byte) int {
-    _, err := ParseStmts(string(in))
+	_, err := ParseStmts(string(in))
 
-    if err == nil {
-        return fuzz_interesting
-    }
+	if err == nil {
+		return fuzzInteresting
+	}
 
-    return fuzz_discard
+	return fuzzDiscard
 }