diff --git a/pdb-plotting/src/main/java/org/lucares/pdb/plot/api/ParallelRequestsAggregator.java b/pdb-plotting/src/main/java/org/lucares/pdb/plot/api/ParallelRequestsAggregator.java
index 681b46b..96aae69 100644
--- a/pdb-plotting/src/main/java/org/lucares/pdb/plot/api/ParallelRequestsAggregator.java
+++ b/pdb-plotting/src/main/java/org/lucares/pdb/plot/api/ParallelRequestsAggregator.java
@@ -14,6 +14,10 @@ import org.slf4j.LoggerFactory;
 
 public class ParallelRequestsAggregator implements CustomAggregator {
 
+	private static final char NEWLINE = '\n';
+
+	private static final char SEPARATOR = ',';
+
 	private static final Logger METRICS_LOGGER = LoggerFactory
 			.getLogger("org.lucares.metrics.aggregator.parallelRequests");
 
@@ -23,9 +27,12 @@ public class ParallelRequestsAggregator implements CustomAggregator {
 
 	private final long fromEpochMilli;
 
+	private final long toEpochMilli;
+
 	public ParallelRequestsAggregator(final Path tmpDir, final long fromEpochMilli, final long toEpochMilli) {
 		this.tmpDir = tmpDir;
 		this.fromEpochMilli = fromEpochMilli;
+		this.toEpochMilli = toEpochMilli;
 
 		if ((toEpochMilli - fromEpochMilli) > 3600 * 1000) {
 			throw new IllegalArgumentException("The " + ParallelRequestsAggregator.class.getSimpleName()
@@ -51,8 +58,6 @@ public class ParallelRequestsAggregator implements CustomAggregator {
 	public AggregatedData getAggregatedData() throws IOException {
 
 		final long start = System.nanoTime();
-		final char separator = ',';
-		final char newline = '\n';
 
 		final File dataFile = File.createTempFile("data", ".dat", tmpDir.toFile());
 		try (final Writer output = new BufferedWriter(
@@ -60,19 +65,22 @@ public class ParallelRequestsAggregator implements CustomAggregator {
 
 			final StringBuilder data = new StringBuilder();
 
+			// first and last value should be 0, or gnuplot will draw a diagonal line
+			appendTimeAndValue(data, fromEpochMilli, 0);
+
 			int value = 0;
 			for (int i = 0; i < increments.length - 1; i++) {
 				final int increment = increments[i];
 				final int nextIncrement = increments[i + 1];
 				if (increment != 0 || nextIncrement != 0) {
 					value += increment;
-					data.append(String.format("%.3f", (fromEpochMilli + i) / 1000.0));
-					data.append(separator);
-					data.append(value);
-					data.append(newline);
+					appendTimeAndValue(data, fromEpochMilli + i, value);
 				}
 			}
 
+			// first and last value should be 0, or gnuplot will draw a diagonal line
+			appendTimeAndValue(data, toEpochMilli, 0);
+
 			output.write(data.toString());
 
 		}
@@ -83,4 +91,11 @@ public class ParallelRequestsAggregator implements CustomAggregator {
 		return new AggregatedData(title, dataFile);
 	}
 
+	private void appendTimeAndValue(final StringBuilder builder, final long timeEpochMilli, final int value) {
+		builder.append(String.format("%.3f", timeEpochMilli / 1000.0));
+		builder.append(SEPARATOR);
+		builder.append(value);
+		builder.append(NEWLINE);
+	}
+
 }