diff --git a/maven-resolver-impl/src/main/java/org/eclipse/aether/internal/impl/filter/ruletree/GroupTree.java b/maven-resolver-impl/src/main/java/org/eclipse/aether/internal/impl/filter/ruletree/GroupTree.java
index b4e29dfbd..87d0023b1 100644
--- a/maven-resolver-impl/src/main/java/org/eclipse/aether/internal/impl/filter/ruletree/GroupTree.java
+++ b/maven-resolver-impl/src/main/java/org/eclipse/aether/internal/impl/filter/ruletree/GroupTree.java
@@ -126,7 +126,7 @@ public boolean acceptedGroupId(String groupId) {
             }
             if (currentNode.isStop() && groupElements.equals(current)) {
                 accepted = currentNode.isAllow();
-            } else if (!currentNode.isStop()) {
+            } else if (!currentNode.isStop() && currentNode.isAllow() != null) {
                 accepted = currentNode.isAllow();
             }
         }
diff --git a/maven-resolver-impl/src/test/java/org/eclipse/aether/internal/impl/filter/ruletree/GroupTreeTest.java b/maven-resolver-impl/src/test/java/org/eclipse/aether/internal/impl/filter/ruletree/GroupTreeTest.java
index 1cdecd136..b47d54d9a 100644
--- a/maven-resolver-impl/src/test/java/org/eclipse/aether/internal/impl/filter/ruletree/GroupTreeTest.java
+++ b/maven-resolver-impl/src/test/java/org/eclipse/aether/internal/impl/filter/ruletree/GroupTreeTest.java
@@ -169,4 +169,37 @@ void implicitAndExplicitDefaultIsSame() {
 
         assertEquals(implicitResults, explicitResults);
     }
+
+    @Test
+    void gh1703One() {
+        GroupTree groupTree;
+
+        // REPRODUCER as given
+        groupTree = new GroupTree("root");
+        // this is redundant, as 'org.apache' IMPLIES 'org.apache.maven.plugins'
+        groupTree.loadNodes(Stream.of("# comment", "", "org.apache", "org.apache.maven.plugins"));
+
+        assertTrue(groupTree.acceptedGroupId("org.apache")); // this is given
+        assertTrue(groupTree.acceptedGroupId("org.apache.maven")); // implied by first
+        assertTrue(groupTree.acceptedGroupId("org.apache.maven.plugins")); // implied by first (line is redundant)
+        assertTrue(groupTree.acceptedGroupId("org.apache.maven.plugins.foo")); // implied by first
+
+        // FIXED
+        groupTree = new GroupTree("root");
+        groupTree.loadNodes(Stream.of("# comment", "", "=org.apache", "org.apache.maven.plugins"));
+
+        assertTrue(groupTree.acceptedGroupId("org.apache")); // this is given (=)
+        assertFalse(groupTree.acceptedGroupId("org.apache.maven")); // not allowed
+        assertTrue(groupTree.acceptedGroupId("org.apache.maven.plugins")); // this is given (and below)
+        assertTrue(groupTree.acceptedGroupId("org.apache.maven.plugins.foo")); // implied by above
+
+        // MIXED
+        groupTree = new GroupTree("root");
+        groupTree.loadNodes(Stream.of("# comment", "", "org.apache", "!=org.apache.maven.plugins"));
+
+        assertTrue(groupTree.acceptedGroupId("org.apache")); // this is given
+        assertTrue(groupTree.acceptedGroupId("org.apache.maven")); // implied by first
+        assertFalse(groupTree.acceptedGroupId("org.apache.maven.plugins")); // this is given (!=)
+        assertTrue(groupTree.acceptedGroupId("org.apache.maven.plugins.foo")); // implied by first
+    }
 }