diff --git a/module/spring-boot-grpc-client/src/main/java/org/springframework/boot/grpc/client/autoconfigure/ServiceConfig.java b/module/spring-boot-grpc-client/src/main/java/org/springframework/boot/grpc/client/autoconfigure/ServiceConfig.java
index c7520906b23..c00b52259f9 100644
--- a/module/spring-boot-grpc-client/src/main/java/org/springframework/boot/grpc/client/autoconfigure/ServiceConfig.java
+++ b/module/spring-boot-grpc-client/src/main/java/org/springframework/boot/grpc/client/autoconfigure/ServiceConfig.java
@@ -87,7 +87,8 @@ public record ServiceConfig(@Nullable List<LoadBalancingConfig> loadbalancing, @
 	}
 
 	static String durationString(Duration duration) {
-		return duration.getSeconds() + "." + duration.getNano() + "s";
+		return (duration.getNano() == 0) ? "%ds".formatted(duration.getSeconds())
+				: "%d.%09ds".formatted(duration.getSeconds(), duration.getNano());
 	}
 
 	static String bytesString(DataSize dataSize) {
diff --git a/module/spring-boot-grpc-client/src/test/java/org/springframework/boot/grpc/client/autoconfigure/ServiceConfigTests.java b/module/spring-boot-grpc-client/src/test/java/org/springframework/boot/grpc/client/autoconfigure/ServiceConfigTests.java
index dff92d54a9d..ed33d5305ce 100644
--- a/module/spring-boot-grpc-client/src/test/java/org/springframework/boot/grpc/client/autoconfigure/ServiceConfigTests.java
+++ b/module/spring-boot-grpc-client/src/test/java/org/springframework/boot/grpc/client/autoconfigure/ServiceConfigTests.java
@@ -255,7 +255,7 @@ class ServiceConfigTests {
 			      method: m-one
 			    retry:
 			      max-attempts: 2
-			      initial-backoff: 1m
+			      initial-backoff: 50ms
 			      max-backoff: 1h
 			      backoff-multiplier: 2.5
 			      per-attempt-receive-timeout: 2s
@@ -268,7 +268,7 @@ class ServiceConfigTests {
 		Map<String, ?> serviceMethodMap = getServiceMethodMap(map, true);
 		Object methodInfo = serviceMethodMap.get("s-one/m-one");
 		assertThat(methodInfo).extracting("retryPolicy.maxAttempts").isEqualTo(2);
-		assertThat(methodInfo).extracting("retryPolicy.initialBackoffNanos").isEqualTo(Duration.ofMinutes(1).toNanos());
+		assertThat(methodInfo).extracting("retryPolicy.initialBackoffNanos").isEqualTo(Duration.ofMillis(50).toNanos());
 		assertThat(methodInfo).extracting("retryPolicy.maxBackoffNanos").isEqualTo(Duration.ofHours(1).toNanos());
 		assertThat(methodInfo).extracting("retryPolicy.backoffMultiplier").isEqualTo(2.5);
 		assertThat(methodInfo).extracting("retryPolicy.perAttemptRecvTimeoutNanos")