diff --git a/services/git-bridge/src/main/java/uk/ac/ic/wlgitbridge/bridge/repo/FSGitRepoStore.java b/services/git-bridge/src/main/java/uk/ac/ic/wlgitbridge/bridge/repo/FSGitRepoStore.java
index eccfa111ed..cbace4118c 100644
--- a/services/git-bridge/src/main/java/uk/ac/ic/wlgitbridge/bridge/repo/FSGitRepoStore.java
+++ b/services/git-bridge/src/main/java/uk/ac/ic/wlgitbridge/bridge/repo/FSGitRepoStore.java
@@ -76,13 +76,13 @@ public class FSGitRepoStore implements RepoStore {
             String projectName,
             long[] sizePtr
     ) throws IOException {
-        Preconditions.checkArgument(Project.isValidProjectName(projectName));
+        Project.checkValidProjectName(projectName);
         return Tar.bz2.zip(getDotGitForProject(projectName), sizePtr);
     }
 
     @Override
     public void remove(String projectName) throws IOException {
-        Preconditions.checkArgument(Project.isValidProjectName(projectName));
+        Project.checkValidProjectName(projectName);
         FileUtils.deleteDirectory(new File(rootDirectory, projectName));
     }
 
@@ -91,13 +91,22 @@ public class FSGitRepoStore implements RepoStore {
             String projectName,
             InputStream dataStream
     ) throws IOException {
-        Preconditions.checkArgument(Project.isValidProjectName(projectName));
-        Preconditions.checkState(getDirForProject(projectName).mkdirs());
+        Preconditions.checkArgument(
+                Project.isValidProjectName(projectName),
+                "[%s] invalid project name: ",
+                projectName
+        );
+        Preconditions.checkState(
+                getDirForProject(projectName).mkdirs(),
+                "[%s] directories for " +
+                        "evicted project already exist",
+                projectName
+        );
         Tar.bz2.unzip(dataStream, getDirForProject(projectName));
     }
 
     private File getDirForProject(String projectName) {
-        Preconditions.checkArgument(Project.isValidProjectName(projectName));
+        Project.checkValidProjectName(projectName);
         return Paths.get(
                 rootDirectory.getAbsolutePath()
         ).resolve(
@@ -106,7 +115,7 @@ public class FSGitRepoStore implements RepoStore {
     }
 
     private File getDotGitForProject(String projectName) {
-        Preconditions.checkArgument(Project.isValidProjectName(projectName));
+        Project.checkValidProjectName(projectName);
         return Paths.get(
                 rootDirectory.getAbsolutePath()
         ).resolve(
@@ -119,7 +128,12 @@ public class FSGitRepoStore implements RepoStore {
     private File initRootGitDirectory(String rootGitDirectoryPath) {
         File rootGitDirectory = new File(rootGitDirectoryPath);
         rootGitDirectory.mkdirs();
-        Preconditions.checkArgument(rootGitDirectory.isDirectory());
+        Preconditions.checkArgument(
+                rootGitDirectory.isDirectory(),
+                "given root git directory " +
+                        "is not a directory: %s",
+                rootGitDirectory.getAbsolutePath()
+        );
         return rootGitDirectory;
     }
 
diff --git a/services/git-bridge/src/main/java/uk/ac/ic/wlgitbridge/bridge/swap/job/SwapJobImpl.java b/services/git-bridge/src/main/java/uk/ac/ic/wlgitbridge/bridge/swap/job/SwapJobImpl.java
index 3513665bf4..ddf309786a 100644
--- a/services/git-bridge/src/main/java/uk/ac/ic/wlgitbridge/bridge/swap/job/SwapJobImpl.java
+++ b/services/git-bridge/src/main/java/uk/ac/ic/wlgitbridge/bridge/swap/job/SwapJobImpl.java
@@ -158,7 +158,7 @@ public class SwapJobImpl implements SwapJob {
      */
     @Override
     public void evict(String projName) throws IOException {
-        Preconditions.checkNotNull(projName);
+        Preconditions.checkNotNull(projName, "projName was null");
         Log.info("Evicting project: {}", projName);
         try (LockGuard __ = lock.lockGuard(projName)) {
             long[] sizePtr = new long[1];
diff --git a/services/git-bridge/src/main/java/uk/ac/ic/wlgitbridge/util/Project.java b/services/git-bridge/src/main/java/uk/ac/ic/wlgitbridge/util/Project.java
index 3c3b4239a1..4e091e2489 100644
--- a/services/git-bridge/src/main/java/uk/ac/ic/wlgitbridge/util/Project.java
+++ b/services/git-bridge/src/main/java/uk/ac/ic/wlgitbridge/util/Project.java
@@ -1,5 +1,7 @@
 package uk.ac.ic.wlgitbridge.util;
 
+import com.google.common.base.Preconditions;
+
 /**
  * Created by winston on 23/08/2016.
  */
@@ -10,4 +12,9 @@ public class Project {
                 && !projectName.startsWith(".");
     }
 
+    public static void checkValidProjectName(String projectName) {
+        Preconditions.checkArgument(isValidProjectName(projectName),
+                "[%s] invalid project name", projectName);
+    }
+
 }