diff --git a/api/src/main/java/org/apache/cloudstack/api/command/admin/acl/project/ListProjectRolesCmd.java b/api/src/main/java/org/apache/cloudstack/api/command/admin/acl/project/ListProjectRolesCmd.java
index dedbb410ea56..6ab7075cb751 100644
--- a/api/src/main/java/org/apache/cloudstack/api/command/admin/acl/project/ListProjectRolesCmd.java
+++ b/api/src/main/java/org/apache/cloudstack/api/command/admin/acl/project/ListProjectRolesCmd.java
@@ -21,6 +21,7 @@
 import java.util.Collections;
 import java.util.List;
 
+import com.cloud.exception.InvalidParameterValueException;
 import org.apache.cloudstack.acl.ProjectRole;
 import org.apache.cloudstack.acl.RoleType;
 import org.apache.cloudstack.api.APICommand;
@@ -55,7 +56,6 @@ public class ListProjectRolesCmd extends BaseListCmd {
     /////////////////// Accessors ///////////////////////
     /////////////////////////////////////////////////////
 
-
     public Long getProjectRoleId() { return projectRoleId; }
 
     public Long getProjectId() {
@@ -72,7 +72,10 @@ public String getRoleName() {
 
     @Override
     public void execute() {
-        List<ProjectRole> projectRoles = new ArrayList<>();
+        if (getProjectId() != null && _projectService.getProject(getProjectId()) == null) {
+            throw new InvalidParameterValueException("Failed to find project by ID.");
+        }
+        List<ProjectRole> projectRoles;
         if (getProjectId() != null && getProjectRoleId() != null) {
             projectRoles = Collections.singletonList(projRoleService.findProjectRole(getProjectRoleId(), getProjectId()));
         } else if (StringUtils.isNotBlank(getRoleName())) {
diff --git a/server/src/main/java/org/apache/cloudstack/acl/ProjectRoleManagerImpl.java b/server/src/main/java/org/apache/cloudstack/acl/ProjectRoleManagerImpl.java
index 91bbb349a07e..6c8b952ddf86 100644
--- a/server/src/main/java/org/apache/cloudstack/acl/ProjectRoleManagerImpl.java
+++ b/server/src/main/java/org/apache/cloudstack/acl/ProjectRoleManagerImpl.java
@@ -168,9 +168,9 @@ public ProjectRole findProjectRole(Long roleId, Long projectId) {
 
     @Override
     public List<ProjectRole> findProjectRoles(Long projectId, String keyword) {
-        if (projectId == null || projectId < 1L || projectDao.findById(projectId) == null) {
-            logger.warn("Invalid project ID provided");
-            return null;
+        if (projectId == null) {
+            logger.warn("Invalid project ID provided; thus, an empty list is being returned.");
+            return Collections.emptyList();
         }
         return ListUtils.toListOfInterface(projRoleDao.findAllRoles(projectId, keyword));
     }