diff --git a/services/git-bridge/pom.xml b/services/git-bridge/pom.xml
index aef616873b..89b4ff3a9a 100644
--- a/services/git-bridge/pom.xml
+++ b/services/git-bridge/pom.xml
@@ -123,6 +123,12 @@
             <artifactId>slf4j-simple</artifactId>
             <version>1.7.13</version>
         </dependency>
+        <dependency>
+            <groupId>com.google.guava</groupId>
+            <artifactId>guava</artifactId>
+            <version>19.0</version>
+        </dependency>
+
         <dependency>
             <groupId>org.mock-server</groupId>
             <artifactId>mockserver-netty</artifactId>
diff --git a/services/git-bridge/src/main/java/uk/ac/ic/wlgitbridge/snapshot/push/PostbackManager.java b/services/git-bridge/src/main/java/uk/ac/ic/wlgitbridge/snapshot/push/PostbackManager.java
index 6dca0b6b3d..3cc598b44b 100644
--- a/services/git-bridge/src/main/java/uk/ac/ic/wlgitbridge/snapshot/push/PostbackManager.java
+++ b/services/git-bridge/src/main/java/uk/ac/ic/wlgitbridge/snapshot/push/PostbackManager.java
@@ -1,10 +1,13 @@
 package uk.ac.ic.wlgitbridge.snapshot.push;
 
-import uk.ac.ic.wlgitbridge.snapshot.push.exception.*;
-import uk.ac.ic.wlgitbridge.util.Log;
+import com.google.common.base.Preconditions;
+import uk.ac.ic.wlgitbridge.snapshot.push.exception.InvalidPostbackKeyException;
+import uk.ac.ic.wlgitbridge.snapshot.push.exception.SnapshotPostException;
+import uk.ac.ic.wlgitbridge.snapshot.push.exception.UnexpectedPostbackException;
 
 import java.math.BigInteger;
 import java.security.SecureRandom;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
 
@@ -14,11 +17,17 @@ import java.util.Map;
 public class PostbackManager {
 
     private final SecureRandom random;
-    private final Map<String, PostbackPromise> postbackContentsTable;
+    final Map<String, PostbackPromise> postbackContentsTable;
+
+    PostbackManager(SecureRandom random) {
+        this.random = random;
+        postbackContentsTable = Collections.synchronizedMap(
+                new HashMap<String, PostbackPromise>()
+        );
+    }
 
     public PostbackManager() {
-        random = new SecureRandom();
-        postbackContentsTable = new HashMap<String, PostbackPromise>();
+        this(new SecureRandom());
     }
 
     public int waitForVersionIdOrThrow(String projectName)
@@ -26,10 +35,7 @@ public class PostbackManager {
         try {
             PostbackPromise postbackPromise =
                     postbackContentsTable.get(projectName);
-            if (postbackPromise == null) {
-                Log.warn("[{}] PostbackPromise was null.", projectName);
-                throw new InternalErrorException();
-            }
+            Preconditions.checkNotNull(postbackPromise);
             return postbackPromise.waitForPostback();
         } finally {
             postbackContentsTable.remove(projectName);
@@ -56,7 +62,7 @@ public class PostbackManager {
 
     private PostbackPromise getPostbackForProject(String projectName)
             throws UnexpectedPostbackException {
-        PostbackPromise contents = postbackContentsTable.remove(projectName);
+        PostbackPromise contents = postbackContentsTable.get(projectName);
         if (contents == null) {
             throw new UnexpectedPostbackException();
         }
diff --git a/services/git-bridge/src/test/java/uk/ac/ic/wlgitbridge/snapshot/push/PostbackManagerTest.java b/services/git-bridge/src/test/java/uk/ac/ic/wlgitbridge/snapshot/push/PostbackManagerTest.java
index f552a4a82a..8575127064 100644
--- a/services/git-bridge/src/test/java/uk/ac/ic/wlgitbridge/snapshot/push/PostbackManagerTest.java
+++ b/services/git-bridge/src/test/java/uk/ac/ic/wlgitbridge/snapshot/push/PostbackManagerTest.java
@@ -6,6 +6,8 @@ import uk.ac.ic.wlgitbridge.snapshot.push.exception.InternalErrorException;
 import uk.ac.ic.wlgitbridge.snapshot.push.exception.SnapshotPostException;
 import uk.ac.ic.wlgitbridge.snapshot.push.exception.UnexpectedPostbackException;
 
+import static org.junit.Assert.*;
+
 /**
  * Created by winston on 05/04/2016.
  */
@@ -20,7 +22,7 @@ public class PostbackManagerTest {
         String key = postbackManager.makeKeyForProject("proj");
         postbackManager.postVersionIDForProject("proj", 1, key);
         int versionId = postbackManager.waitForVersionIdOrThrow("proj");
-        Assert.assertEquals("Version id didn't match posted", 1, versionId);
+        assertEquals("Version id didn't match posted", 1, versionId);
     }
 
     @Test
@@ -38,4 +40,20 @@ public class PostbackManagerTest {
         Assert.fail("Exception wasn't thrown as required");
     }
 
+    @Test
+    public void testTableConsistency() throws UnexpectedPostbackException,
+                                              SnapshotPostException {
+        String key1 = postbackManager.makeKeyForProject("proj1");
+        assertEquals(1, postbackManager.postbackContentsTable.size());
+        String key2 = postbackManager.makeKeyForProject("proj2");
+        assertEquals(2, postbackManager.postbackContentsTable.size());
+        postbackManager.postVersionIDForProject("proj1", 1, key1);
+        postbackManager.postVersionIDForProject("proj2", 1, key2);
+        assertEquals(2, postbackManager.postbackContentsTable.size());
+        postbackManager.waitForVersionIdOrThrow("proj1");
+        assertEquals(1, postbackManager.postbackContentsTable.size());
+        postbackManager.waitForVersionIdOrThrow("proj2");
+        Assert.assertTrue(postbackManager.postbackContentsTable.isEmpty());
+    }
+
 }