diff --git a/base-test/org.eclipse.jdt.groovy.core.tests.builder/src/org/eclipse/jdt/core/groovy/tests/search/GenericInferencingTests.java b/base-test/org.eclipse.jdt.groovy.core.tests.builder/src/org/eclipse/jdt/core/groovy/tests/search/GenericInferencingTests.java
index 88d0734bbf..0564ae057c 100644
--- a/base-test/org.eclipse.jdt.groovy.core.tests.builder/src/org/eclipse/jdt/core/groovy/tests/search/GenericInferencingTests.java
+++ b/base-test/org.eclipse.jdt.groovy.core.tests.builder/src/org/eclipse/jdt/core/groovy/tests/search/GenericInferencingTests.java
@@ -665,14 +665,60 @@ public void testMapOfMaps() {
     }
 
     @Test
-    public void testTypeExtendsMap() {
+    public void testTypeExtendsMap1() {
         String contents =
-            "interface Config extends Map<String, Number> {}\n" +
-            "void meth(Config config) {\n" +
+            "interface I extends Map<String, Number> {}\n" +
+            "void m(I config) {\n" +
             "  def xxx = config.whatever\n" +
+            "  def yyy = config['whatever']\n" +
             "}\n";
 
         assertType(contents, "xxx", "java.lang.Number");
+        assertType(contents, "yyy", "java.lang.Number");
+    }
+
+    @Test
+    public void testTypeExtendsMap2() {
+        String contents =
+            "interface I extends Map<String, Number> {}\n" +
+            "abstract class A implements I {}\n" +
+            "void m(A config) {\n" +
+            "  def xxx = config.whatever\n" +
+            "  def yyy = config['whatever']\n" +
+            "}\n";
+
+        assertType(contents, "xxx", "java.lang.Number");
+        assertType(contents, "yyy", "java.lang.Number");
+    }
+
+    @Test // https://github.com/groovy/groovy-eclipse/issues/1189
+    public void testTypeExtendsMap3() {
+        String contents =
+            "interface I extends Map<String, Number> {}\n" +
+            "abstract class A implements I {}\n" +
+            "class C extends A {}\n" +
+            "void m(C config) {\n" +
+            "  def xxx = config.whatever\n" +
+            "  def yyy = config['whatever']\n" +
+            "}\n";
+
+        assertType(contents, "xxx", "java.lang.Number");
+        assertType(contents, "yyy", "java.lang.Number");
+    }
+
+    @Test // https://github.com/groovy/groovy-eclipse/issues/1189
+    public void testTypeExtendsMap4() {
+        String contents =
+            "interface I<T> extends Map<String, T> {}\n" +
+            "abstract class A<U> implements I<U> {}\n" +
+            "class C extends A<Number> {}\n" +
+            "void m(C config) {\n" +
+            "  def xxx = config.whatever\n" +
+            "  def yyy = config['whatever']\n" +
+            "}\n";
+
+        assertType(contents, "xxx", "java.lang.Number");
+        assertType(contents, "yyy", "java.lang.Number");
     }
 
     @Test
diff --git a/base/org.eclipse.jdt.groovy.core/src/org/eclipse/jdt/groovy/core/util/GroovyUtils.java b/base/org.eclipse.jdt.groovy.core/src/org/eclipse/jdt/groovy/core/util/GroovyUtils.java
index aaf77d58d3..0db60c29d3 100644
--- a/base/org.eclipse.jdt.groovy.core/src/org/eclipse/jdt/groovy/core/util/GroovyUtils.java
+++ b/base/org.eclipse.jdt.groovy.core/src/org/eclipse/jdt/groovy/core/util/GroovyUtils.java
@@ -20,6 +20,7 @@
 import java.util.Collections;
 import java.util.Comparator;
 import java.util.HashSet;
+import java.util.LinkedHashSet;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
@@ -50,6 +51,7 @@
 import org.codehaus.groovy.ast.expr.TernaryExpression;
 import org.codehaus.groovy.ast.expr.VariableExpression;
 import org.codehaus.groovy.ast.tools.GeneralUtils;
+import org.codehaus.groovy.ast.tools.GenericsUtils;
 import org.codehaus.groovy.control.CompilePhase;
 import org.codehaus.groovy.runtime.MetaClassHelper;
 import org.codehaus.groovy.transform.ASTTransformation;
@@ -131,6 +133,24 @@ public static String[] splitName(ClassNode node) {
         return new String[] {name.substring(0, Math.max(0, index)), name.substring(index + 1)};
     }
 
+    public static Set<ClassNode> getAllInterfaces(ClassNode node) {
+        Set<ClassNode> result = new LinkedHashSet<>();
+        if (node.isInterface()) result.add(node);
+        addAllInterfaces(result, node);
+        return result;
+    }
+
+    private static void addAllInterfaces(Set<ClassNode> result, ClassNode source) {
+        for (ClassNode face : source.getInterfaces()) {
+            face = GenericsUtils.parameterizeType(source, face);
+            if (result.add(face)) addAllInterfaces(result, face);
+        }
+        ClassNode sc = source.redirect().getUnresolvedSuperClass(false);
+        if (sc != null && !sc.equals(ClassHelper.OBJECT_TYPE)) {
+            addAllInterfaces(result, GenericsUtils.parameterizeType(source, sc));
+        }
+    }
+
     public static Stream<AnnotationNode> getAnnotations(AnnotatedNode node, String name) {
         return node.getAnnotations().stream().filter(an -> an.getClassNode().getName().equals(name));
     }
diff --git a/base/org.eclipse.jdt.groovy.core/src/org/eclipse/jdt/groovy/search/CategoryTypeLookup.java b/base/org.eclipse.jdt.groovy.core/src/org/eclipse/jdt/groovy/search/CategoryTypeLookup.java
index c94cb7607a..96c73a5c51 100644
--- a/base/org.eclipse.jdt.groovy.core/src/org/eclipse/jdt/groovy/search/CategoryTypeLookup.java
+++ b/base/org.eclipse.jdt.groovy.core/src/org/eclipse/jdt/groovy/search/CategoryTypeLookup.java
@@ -92,7 +92,7 @@ public TypeLookupResult lookupType(final Expression node, final VariableScope sc
                     ClassNode resolvedType = method.getReturnType();
                     // getAt(Object,String):Object supersedes getAt(Map<K,V>,Object):V when first param is String or GString; restore return type V for user experience
                     if ("getAt".equals(simpleName) && VariableScope.OBJECT_CLASS_NODE.equals(resolvedType) && isOrImplements(selfType, VariableScope.MAP_CLASS_NODE)) {
-                        for (ClassNode face : selfType.getAllInterfaces()) {
+                        for (ClassNode face : GroovyUtils.getAllInterfaces(selfType)) {
                             if (face.equals(VariableScope.MAP_CLASS_NODE)) { // Map<K,V>
                                 GenericsType[] generics = GroovyUtils.getGenericsTypes(face);
                                 if (generics.length == 2) resolvedType = generics[1].getType();
diff --git a/base/org.eclipse.jdt.groovy.core/src/org/eclipse/jdt/groovy/search/SimpleTypeLookup.java b/base/org.eclipse.jdt.groovy.core/src/org/eclipse/jdt/groovy/search/SimpleTypeLookup.java
index b44283afad..2b16b4edbf 100644
--- a/base/org.eclipse.jdt.groovy.core/src/org/eclipse/jdt/groovy/search/SimpleTypeLookup.java
+++ b/base/org.eclipse.jdt.groovy.core/src/org/eclipse/jdt/groovy/search/SimpleTypeLookup.java
@@ -633,7 +633,7 @@ protected ASTNode findDeclaration(final String name, final ClassNode declaringTy
                 resolvedType = VariableScope.VOID_CLASS_NODE;
             } else {
                 resolvedType = VariableScope.OBJECT_CLASS_NODE;
-                for (ClassNode face : declaringType.getAllInterfaces()) {
+                for (ClassNode face : GroovyUtils.getAllInterfaces(declaringType)) {
                     if (face.equals(VariableScope.MAP_CLASS_NODE)) { // Map<K,V>
                         GenericsType[] generics = GroovyUtils.getGenericsTypes(face);
                         if (generics.length == 2) resolvedType = generics[1].getType();