diff --git a/spring-cloud-sleuth-core/src/main/java/org/springframework/cloud/sleuth/instrument/web/ZipkinHttpSpanExtractor.java b/spring-cloud-sleuth-core/src/main/java/org/springframework/cloud/sleuth/instrument/web/ZipkinHttpSpanExtractor.java
index 5cfe870ea..91906e711 100644
--- a/spring-cloud-sleuth-core/src/main/java/org/springframework/cloud/sleuth/instrument/web/ZipkinHttpSpanExtractor.java
+++ b/spring-cloud-sleuth-core/src/main/java/org/springframework/cloud/sleuth/instrument/web/ZipkinHttpSpanExtractor.java
@@ -1,16 +1,16 @@
 package org.springframework.cloud.sleuth.instrument.web;
 
+import java.lang.invoke.MethodHandles;
+import java.util.Map;
+import java.util.Random;
+import java.util.regex.Pattern;
+
 import org.apache.commons.logging.LogFactory;
 import org.springframework.cloud.sleuth.Span;
 import org.springframework.cloud.sleuth.SpanTextMap;
 import org.springframework.cloud.sleuth.util.TextMapUtil;
 import org.springframework.util.StringUtils;
 
-import java.lang.invoke.MethodHandles;
-import java.util.Map;
-import java.util.Random;
-import java.util.regex.Pattern;
-
 /**
  * Default implementation, compatible with Zipkin propagation.
  *
@@ -35,11 +35,11 @@ public class ZipkinHttpSpanExtractor implements HttpSpanExtractor {
 	public Span joinTrace(SpanTextMap textMap) {
 		Map<String, String> carrier = TextMapUtil.asMap(textMap);
 		boolean debug = Span.SPAN_SAMPLED.equals(carrier.get(Span.SPAN_FLAGS));
-		if (debug) {
+		if (debug && onlySpanIdIsPresent(carrier)) {
 			// we're only generating Trace ID since if there's no Span ID will assume
-			// that it's equal to Trace ID
+			// that it's equal to Trace ID - we're trying to fix a malformed request
 			generateIdIfMissing(carrier, Span.TRACE_ID_NAME);
-		} else if (carrier.get(Span.TRACE_ID_NAME) == null) {
+		} else if (traceIdIsMissing(carrier)) {
 			// can't build a Span without trace id
 			return null;
 		}
@@ -55,6 +55,18 @@ public class ZipkinHttpSpanExtractor implements HttpSpanExtractor {
 		}
 	}
 
+	private boolean onlySpanIdIsPresent(Map<String, String> carrier) {
+		return traceIdIsMissing(carrier) && spanIdIsPresent(carrier);
+	}
+
+	private boolean traceIdIsMissing(Map<String, String> carrier) {
+		return carrier.get(Span.TRACE_ID_NAME) == null;
+	}
+
+	private boolean spanIdIsPresent(Map<String, String> carrier) {
+		return carrier.get(Span.SPAN_ID_NAME) != null;
+	}
+
 	private void generateIdIfMissing(Map<String, String> carrier, String key) {
 		if (!carrier.containsKey(key)) {
 			carrier.put(key, Span.idToHex(new Random().nextLong()));
diff --git a/spring-cloud-sleuth-core/src/test/java/org/springframework/cloud/sleuth/instrument/web/TraceFilterTests.java b/spring-cloud-sleuth-core/src/test/java/org/springframework/cloud/sleuth/instrument/web/TraceFilterTests.java
index 50cee09dc..a4eaa9d4b 100644
--- a/spring-cloud-sleuth-core/src/test/java/org/springframework/cloud/sleuth/instrument/web/TraceFilterTests.java
+++ b/spring-cloud-sleuth-core/src/test/java/org/springframework/cloud/sleuth/instrument/web/TraceFilterTests.java
@@ -31,7 +31,6 @@ import org.springframework.beans.factory.BeanFactory;
 import org.springframework.cloud.sleuth.DefaultSpanNamer;
 import org.springframework.cloud.sleuth.ErrorParser;
 import org.springframework.cloud.sleuth.ExceptionMessageErrorParser;
-import org.springframework.cloud.sleuth.NoOpSpanReporter;
 import org.springframework.cloud.sleuth.Sampler;
 import org.springframework.cloud.sleuth.Span;
 import org.springframework.cloud.sleuth.SpanReporter;
@@ -447,6 +446,29 @@ public class TraceFilterTests {
 		then(ExceptionUtils.getLastException()).isNull();
 	}
 
+	@Test
+	public void samplesASpanDebugFlagWithInterceptor() throws Exception {
+		this.request = builder()
+				.header(Span.SPAN_FLAGS, 1)
+				.buildRequest(new MockServletContext());
+		this.sampler = new NeverSampler();
+		TraceFilter filter = new TraceFilter(beanFactory());
+
+		filter.doFilter(this.request, this.response, (req, res) -> {
+			// Simulate the TraceHandlerInterceptor
+			req.setAttribute(TraceRequestAttributes.HANDLED_SPAN_REQUEST_ATTR, span);
+			this.filterChain.doFilter(req, res);
+		});
+
+		then(new ListOfSpans(this.spanReporter.getSpans()))
+				.doesNotHaveASpanWithName("http:/parent/")
+				.hasASpanWithName("http:/")
+				.hasSize(1)
+				.allSpansAreExportable();
+		then(TestSpanContextHolder.getCurrentSpan()).isNull();
+		then(ExceptionUtils.getLastException()).isNull();
+	}
+
 	public void verifyParentSpanHttpTags() {
 		verifyParentSpanHttpTags(HttpStatus.OK);
 	}
@@ -487,7 +509,7 @@ public class TraceFilterTests {
 		BDDMockito.given(beanFactory.getBean(Tracer.class)).willReturn(this.tracer);
 		BDDMockito.given(beanFactory.getBean(TraceKeys.class)).willReturn(this.traceKeys);
 		BDDMockito.given(beanFactory.getBean(HttpSpanExtractor.class)).willReturn(this.spanExtractor);
-		BDDMockito.given(beanFactory.getBean(SpanReporter.class)).willReturn(new NoOpSpanReporter());
+		BDDMockito.given(beanFactory.getBean(SpanReporter.class)).willReturn(this.spanReporter);
 		BDDMockito.given(beanFactory.getBean(HttpTraceKeysInjector.class)).willReturn(this.httpTraceKeysInjector);
 		BDDMockito.given(beanFactory.getBean(ErrorParser.class)).willReturn(new ExceptionMessageErrorParser());
 		return beanFactory;