diff --git a/src/main/java/cpath/service/ServiceImpl.java b/src/main/java/cpath/service/ServiceImpl.java
index 8b205ffe..f0d4d462 100644
--- a/src/main/java/cpath/service/ServiceImpl.java
+++ b/src/main/java/cpath/service/ServiceImpl.java
@@ -378,8 +378,8 @@ public ServiceResponse getCommonStream(OutputFormat format,
       return new ErrorResponse(MAINTENANCE, "Waiting for the initialization to complete (try again later)...");
     }
 
-    if (direction == Direction.BOTHSTREAM) {
-      return new ErrorResponse(BAD_REQUEST, "Direction cannot be BOTHSTREAM for the COMMONSTREAM query");
+    if (direction == Direction.BOTHSTREAM || direction == Direction.UNDIRECTED) {
+      return new ErrorResponse(BAD_REQUEST, "COMMONSTREAM graph query direction must be either UPSTREAM or DOWNSTREAM (default)");
     } else if(direction == null) {
       direction = Direction.DOWNSTREAM;
     }
diff --git a/src/main/java/cpath/web/args/CommonStream.java b/src/main/java/cpath/web/args/CommonStream.java
index 9c563a1e..51459c8f 100644
--- a/src/main/java/cpath/web/args/CommonStream.java
+++ b/src/main/java/cpath/web/args/CommonStream.java
@@ -6,14 +6,13 @@
 public class CommonStream extends BaseGraph {
 
   @Schema(
-      description = "Graph search direction (default: UNDIRECTED; cannot be BOTHSTREAM)",
-      example = "undirected"
+      description = "Graph search direction (default: DOWNSTREAM; can be either DOWNSTREAM or UPSTREAM)",
+      example = "downstream"
   )
   private Direction direction;
 
   public CommonStream() {
     super();
-    direction = Direction.UNDIRECTED;
   }
 
   public Direction getDirection() {
@@ -21,9 +20,7 @@ public Direction getDirection() {
   }
 
   public void setDirection(String direction) {
-    Direction dir = Direction.typeOf(direction); //null when illegal value (also handles empty/null and register/case)
-    //also exclude/replace BOTHSTREAM value
-    this.direction = (dir != null && dir != Direction.BOTHSTREAM) ? dir : Direction.UNDIRECTED;
+    this.direction = Direction.typeOf(direction); //null when illegal value
   }
 
   @Override
diff --git a/src/main/java/cpath/web/args/Graph.java b/src/main/java/cpath/web/args/Graph.java
index c7cbd95a..209ae11a 100644
--- a/src/main/java/cpath/web/args/Graph.java
+++ b/src/main/java/cpath/web/args/Graph.java
@@ -26,8 +26,8 @@ public class Graph extends BaseGraph {
   private GraphType kind;
 
   @Schema(
-      description = "Graph search direction (default: UNDIRECTED)",
-      example = "undirected"
+      description = "Graph search direction (only for 'neighborhood' and 'commonstream' graph query types; the latter only accepts: 'upstream' or 'downstream')",
+      example = "downstream"
   )
   private Direction direction;
 
@@ -47,7 +47,6 @@ public class Graph extends BaseGraph {
   public Graph() {
     super();
     limitType = LimitType.NORMAL; //for pathsfromto only
-    direction = Direction.UNDIRECTED;
   }
 
   public GraphType getKind() {
@@ -63,8 +62,7 @@ public Direction getDirection() {
   }
 
   public void setDirection(String direction) {
-    Direction dir = Direction.typeOf(direction); //null when illegal value (also handles empty/null and register/case)
-    this.direction = (dir != null) ? dir : Direction.UNDIRECTED;
+    this.direction = Direction.typeOf(direction); //null when illegal value (also handles empty/null and register/case)
   }
 
   public String[] getTarget() {
diff --git a/src/main/java/cpath/web/args/Neighborhood.java b/src/main/java/cpath/web/args/Neighborhood.java
index 53b287ce..e886e4bd 100644
--- a/src/main/java/cpath/web/args/Neighborhood.java
+++ b/src/main/java/cpath/web/args/Neighborhood.java
@@ -13,7 +13,6 @@ public class Neighborhood extends BaseGraph {
 
   public Neighborhood() {
     super();
-    direction = Direction.UNDIRECTED;
   }
 
   public Direction getDirection() {
@@ -21,15 +20,15 @@ public Direction getDirection() {
   }
 
   public void setDirection(String direction) {
-    Direction dir = Direction.typeOf(direction); //null when illegal value (also handles empty/null and register/case)
-    this.direction = (dir != null) ? dir : Direction.UNDIRECTED;
+    this.direction = Direction.typeOf(direction); //null when illegal value (also handles empty/null and register/case)
   }
 
   @Override
   public String toString() {
     StringBuilder sb = new StringBuilder(super.toString());
-    if (direction != null)
+    if (direction != null) {
       sb.append("; dir:").append(direction);
+    }
     return sb.toString();
   }