diff --git a/src/main/java/org/folio/linked/data/mapper/dto/monograph/TopResourceMapperUnit.java b/src/main/java/org/folio/linked/data/mapper/dto/monograph/TopResourceMapperUnit.java
index 4bc32aa2..2795389f 100644
--- a/src/main/java/org/folio/linked/data/mapper/dto/monograph/TopResourceMapperUnit.java
+++ b/src/main/java/org/folio/linked/data/mapper/dto/monograph/TopResourceMapperUnit.java
@@ -34,6 +34,7 @@ protected List<String> getPrimaryMainTitles(List<TitleFieldRequestTitleInner> ti
       .map(PrimaryTitleField.class::cast)
       .map(PrimaryTitleField::getPrimaryTitle)
       .map(pt -> join(" ", getFirstValue(pt::getMainTitle), getFirstValue(pt::getSubTitle)))
+      .map(String::trim)
       .toList();
   }
 }
diff --git a/src/main/java/org/folio/linked/data/mapper/dto/monograph/common/title/TitleMapperUnit.java b/src/main/java/org/folio/linked/data/mapper/dto/monograph/common/title/TitleMapperUnit.java
index 00dfa4f9..646c6b83 100644
--- a/src/main/java/org/folio/linked/data/mapper/dto/monograph/common/title/TitleMapperUnit.java
+++ b/src/main/java/org/folio/linked/data/mapper/dto/monograph/common/title/TitleMapperUnit.java
@@ -1,5 +1,8 @@
 package org.folio.linked.data.mapper.dto.monograph.common.title;
 
+import static org.apache.commons.lang3.StringUtils.isBlank;
+import static java.lang.String.join;
+
 import java.util.Set;
 import org.folio.linked.data.domain.dto.InstanceRequest;
 import org.folio.linked.data.domain.dto.InstanceResponse;
@@ -22,6 +25,6 @@ public Set<Class<?>> supportedParents() {
   }
 
   protected String getLabel(String mainTitle, String subTitle) {
-    return String.join(" ", mainTitle, subTitle);
+    return isBlank(subTitle) ? mainTitle : join(" ", mainTitle, subTitle);
   }
 }