diff --git a/spring-integration-core/src/main/java/org/springframework/integration/util/SimplePool.java b/spring-integration-core/src/main/java/org/springframework/integration/util/SimplePool.java
index 98239e328c9..010038cf943 100644
--- a/spring-integration-core/src/main/java/org/springframework/integration/util/SimplePool.java
+++ b/spring-integration-core/src/main/java/org/springframework/integration/util/SimplePool.java
@@ -36,6 +36,7 @@
  * demand up to the limit.
  *
  * @author Gary Russell
+ * @author Sergey Bogatyrev
  * @since 2.2
  *
  */
@@ -102,11 +103,9 @@ public synchronized void setPoolSize(int poolSize) {
 					break;
 				}
 				T item = this.available.poll();
-				if (item == null) {
-					this.permits.release();
-					break;
+				if (item != null) {
+					doRemoveItem(item);
 				}
-				doRemoveItem(item);
 				this.poolSize.decrementAndGet();
 				delta++;
 			}
diff --git a/spring-integration-core/src/test/java/org/springframework/integration/util/SimplePoolTests.java b/spring-integration-core/src/test/java/org/springframework/integration/util/SimplePoolTests.java
index 3f6945bbe64..e4482ce3619 100644
--- a/spring-integration-core/src/test/java/org/springframework/integration/util/SimplePoolTests.java
+++ b/spring-integration-core/src/test/java/org/springframework/integration/util/SimplePoolTests.java
@@ -19,7 +19,9 @@
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.fail;
 
+import java.util.ArrayList;
 import java.util.HashSet;
+import java.util.List;
 import java.util.Set;
 import java.util.concurrent.Semaphore;
 import java.util.concurrent.atomic.AtomicBoolean;
@@ -30,6 +32,7 @@
 
 /**
  * @author Gary Russell
+ * @author Sergey Bogatyrev
  * @since 2.2
  *
  */
@@ -147,6 +150,72 @@ public void testDoubleReturn() {
 		assertThat(permits.availablePermits()).isEqualTo(2);
 	}
 
+	@Test
+	public void testSizeUpdateIfNotAllocated() {
+		SimplePool<String> pool = stringPool(10, new HashSet<>(), new AtomicBoolean());
+		pool.setWaitTimeout(0);
+		pool.setPoolSize(5);
+		assertThat(pool.getPoolSize()).isEqualTo(5);
+
+		// allocating all available items to check permits
+		Set<String> allocatedItems = new HashSet<>();
+		for (int i = 0; i < 5; i++) {
+			allocatedItems.add(pool.getItem());
+		}
+		assertThat(allocatedItems).hasSize(5);
+
+		// no more items can be allocated (indirect check of permits)
+		try {
+			pool.getItem();
+			fail("No more items should be allocated");
+		}
+		catch (PoolItemNotAvailableException e) {
+			// permits state correctly
+		}
+	}
+
+	@Test
+	public void testSizeUpdateIfAllocated() {
+		SimplePool<String> pool = stringPool(10, new HashSet<>(), new AtomicBoolean());
+		pool.setWaitTimeout(0);
+		List<String> allocated = new ArrayList<>();
+		for (int i = 0; i < 10; i++) {
+			allocated.add(pool.getItem());
+		}
+
+		// release only 2 items
+		for (int i = 0; i < 2; i++) {
+			pool.releaseItem(allocated.get(i));
+		}
+
+		// trying to reduce pool size
+		pool.setPoolSize(5);
+
+		// at this moment the actual pool size can be reduced only partially, because
+		// only 2 items have been released, so 8 items are in use
+		assertThat(pool.getPoolSize()).isEqualTo(8);
+		assertThat(pool.getAllocatedCount()).isEqualTo(8);
+		assertThat(pool.getIdleCount()).isEqualTo(0);
+
+		// releasing 3 items
+		for (int i = 2; i < 5; i++) {
+			pool.releaseItem(allocated.get(i));
+		}
+
+		// now pool size should be reduced
+		assertThat(pool.getPoolSize()).isEqualTo(5);
+		assertThat(pool.getAllocatedCount()).isEqualTo(5);
+		assertThat(pool.getIdleCount()).isEqualTo(0);
+
+		// no more items can be allocated (indirect check of permits)
+		try {
+			pool.getItem();
+			fail("No more items should be allocated");
+		}
+		catch (PoolItemNotAvailableException e) {
+			// permits state correctly
+		}
+	}
 
 	private SimplePool<String> stringPool(int size, final Set<String> strings,
 			final AtomicBoolean stale) {