diff --git a/build.gradle b/build.gradle
index 4651a9d0..614f96b9 100644
--- a/build.gradle
+++ b/build.gradle
@@ -36,7 +36,7 @@ group = 'io.emeraldpay.dshackle'
 // Version schema:
 //    x.x.x for production, following SemVer model
 //    x.x.x-SNAPSHOT for development
-version = '0.14.0-SNAPSHOT'
+version = '0.15.0-SNAPSHOT'
 
 java {
     sourceCompatibility = JavaVersion.VERSION_13
@@ -177,7 +177,7 @@ jib {
         }
     }
     container {
-        jvmFlags = ['-Xms1024m', '-XX:MaxRAMPercentage=60']
+        jvmFlags = ['-Xms1024m', '-Xmx4g']
         mainClass = 'io.emeraldpay.dshackle.StarterKt'
         args = []
         ports = ['2448', '2449', '8545']
diff --git a/src/main/kotlin/io/emeraldpay/dshackle/upstream/AbstractHead.kt b/src/main/kotlin/io/emeraldpay/dshackle/upstream/AbstractHead.kt
index f93152c0..77318863 100644
--- a/src/main/kotlin/io/emeraldpay/dshackle/upstream/AbstractHead.kt
+++ b/src/main/kotlin/io/emeraldpay/dshackle/upstream/AbstractHead.kt
@@ -53,11 +53,12 @@ abstract class AbstractHead(
                 val delay = System.currentTimeMillis() - lastHeadUpdated
                 if (delay > awaitHeadTimeoutMs) {
                     log.warn("No head updates for $delay ms @ ${this.javaClass} - restart")
-                    try {
-                        lock.tryLock()
-                        start()
-                    } finally {
-                        lock.unlock()
+                    if (lock.tryLock()) {
+                        try {
+                            start()
+                        } finally {
+                            lock.unlock()
+                        }
                     }
                 }
             }, 300, 30, TimeUnit.SECONDS