diff --git a/src/main/groovy/com/avast/gradle/dockercompose/ComposeSettings.groovy b/src/main/groovy/com/avast/gradle/dockercompose/ComposeSettings.groovy
index 2a7abce..4a949c4 100644
--- a/src/main/groovy/com/avast/gradle/dockercompose/ComposeSettings.groovy
+++ b/src/main/groovy/com/avast/gradle/dockercompose/ComposeSettings.groovy
@@ -97,10 +97,10 @@ abstract class ComposeSettings {
                 return customProjectName
             }
             else if (projectNamePrefix) {
-                return "${projectNamePrefix}_${nestedName}"
+                return nestedName ? "${projectNamePrefix}_${nestedName}" : projectNamePrefix
             }
             else {
-                return "${safeProjectNamePrefix}_${nestedName}"
+                return nestedName ? "${safeProjectNamePrefix}_${nestedName}" : safeProjectNamePrefix
             }
         }).map{ String projectName ->
             // docker-compose project names must be lowercase