diff --git a/spring-web/src/main/java/org/springframework/web/server/adapter/WebHttpHandlerBuilder.java b/spring-web/src/main/java/org/springframework/web/server/adapter/WebHttpHandlerBuilder.java
index 1b09810ecd..68f0992936 100644
--- a/spring-web/src/main/java/org/springframework/web/server/adapter/WebHttpHandlerBuilder.java
+++ b/spring-web/src/main/java/org/springframework/web/server/adapter/WebHttpHandlerBuilder.java
@@ -198,7 +198,7 @@ public final class WebHttpHandlerBuilder {
 				.forEach(builder::httpHandlerDecorator);
 
 		context.getBeanProvider(ObservationRegistry.class).ifUnique(builder::observationRegistry);
-		context.getBeanProvider(ServerRequestObservationConvention.class).ifUnique(builder::observationConvention);
+		context.getBeanProvider(ServerRequestObservationConvention.class).ifAvailable(builder::observationConvention);
 
 		try {
 			builder.sessionManager(
diff --git a/spring-web/src/test/java/org/springframework/web/server/adapter/WebHttpHandlerBuilderTests.java b/spring-web/src/test/java/org/springframework/web/server/adapter/WebHttpHandlerBuilderTests.java
index 522d8aafb1..c9ed2b8b21 100644
--- a/spring-web/src/test/java/org/springframework/web/server/adapter/WebHttpHandlerBuilderTests.java
+++ b/spring-web/src/test/java/org/springframework/web/server/adapter/WebHttpHandlerBuilderTests.java
@@ -28,6 +28,7 @@ import org.junit.jupiter.api.Test;
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
 
+import org.springframework.beans.factory.NoUniqueBeanDefinitionException;
 import org.springframework.context.annotation.AnnotationConfigApplicationContext;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
@@ -49,6 +50,7 @@ import org.springframework.web.testfixture.http.server.reactive.MockServerHttpRe
 
 import static java.time.Duration.ofMillis;
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
 
 /**
  * Unit tests for {@link WebHttpHandlerBuilder}.
@@ -173,6 +175,14 @@ public class WebHttpHandlerBuilderTests {
 				.that().hasLowCardinalityKeyValue("uri", "UNKNOWN");
 	}
 
+	@Test
+	void shouldRejectDuplicateObservationConvention() {
+		AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(ObservationConfig.class,
+				DuplicateConventionObservationConfig.class);
+		assertThatThrownBy(() -> WebHttpHandlerBuilder.applicationContext(applicationContext).build())
+				.isInstanceOf(NoUniqueBeanDefinitionException.class);
+	}
+
 	private static Mono<Void> writeToResponse(ServerWebExchange exchange, String value) {
 		byte[] bytes = value.getBytes(StandardCharsets.UTF_8);
 		DataBuffer buffer = DefaultDataBufferFactory.sharedInstance.wrap(bytes);
@@ -315,4 +325,14 @@ public class WebHttpHandlerBuilderTests {
 
 	}
 
+	@Configuration
+	static class DuplicateConventionObservationConfig {
+
+		@Bean
+		public ServerRequestObservationConvention duplicateRequestObservationConvention() {
+			return new DefaultServerRequestObservationConvention();
+		}
+
+	}
+
 }