diff --git a/langserver/java/expression-resolver.js b/langserver/java/expression-resolver.js
index 349a135..50cd6a0 100644
--- a/langserver/java/expression-resolver.js
+++ b/langserver/java/expression-resolver.js
@@ -304,8 +304,10 @@ function isTypeAssignable(dest_type, value_type) {
                 }
             }
         }
+    } else if (dest_type instanceof TypeVariableType) {
+        is_assignable = !(value_type instanceof PrimitiveType || value_type instanceof NullType);
     }
-    return is_assignable;
+return is_assignable;
 }
 
 /**
diff --git a/langserver/java/source-types.js b/langserver/java/source-types.js
index de4e81f..cf09d28 100644
--- a/langserver/java/source-types.js
+++ b/langserver/java/source-types.js
@@ -136,7 +136,6 @@ class SourceType extends CEIType {
     }
 
     /**
-     * 
      * @param {JavaType[]} types 
      * @returns {CEIType}
      */
@@ -178,6 +177,7 @@ class SpecialisedSourceType extends CEIType {
      */
     constructor(source_type, typeKind, raw_short_signature, types) {
         super(raw_short_signature, typeKind, source_type.modifiers, source_type.docs);
+        this.source_type = source_type;
         this.typemap = source_type.typemap;
         /** @type {TypeArgument[]} */
         // @ts-ignore
@@ -262,6 +262,25 @@ class SpecialisedSourceType extends CEIType {
             };
         });
     }
+
+    /**
+     * @param {JavaType[]} types 
+     * @returns {CEIType}
+     */
+    specialise(types) {
+        const short_sig = `${this._rawShortSignature}<${types.map(t => t.typeSignature).join('')}>`;
+        if (this.typemap.has(short_sig)) {
+            // @ts-ignore
+            return this.typemap.get(short_sig);
+        }
+        /** @type {'class'|'enum'|'interface'|'@interface'} */
+        // @ts-ignore
+        const typeKind = this.typeKind;
+        const specialised_type = new SpecialisedSourceType(this.source_type, typeKind, this._rawShortSignature, types);
+        this.typemap.set(short_sig, specialised_type);
+        return specialised_type;
+    }
+
 }
 
 class SourceEnumValue extends Field {
diff --git a/langserver/java/validation/non-implemented-interfaces.js b/langserver/java/validation/non-implemented-interfaces.js
index e0fff29..be905d9 100644
--- a/langserver/java/validation/non-implemented-interfaces.js
+++ b/langserver/java/validation/non-implemented-interfaces.js
@@ -1,11 +1,27 @@
 const ParseProblem = require('../parsetypes/parse-problem');
 const { SourceType } = require('../source-types');
-const {CEIType} = require('java-mti');
+const { CEIType, Method} = require('java-mti');
+const {isTypeAssignable} = require('../expression-resolver');
 
 function nonAbstractLabel(label) {
     return label.replace(/\babstract /g, '');
 }
 
+/**
+ * 
+ * @param {Method} impl method implementation
+ * @param {Method} method interface method
+ */
+function isMethodCompatible(impl, method) {
+    const impl_params = impl.parameters;
+    const method_params = method.parameters;
+    if (impl_params.length !== method_params.length) {
+        return false;
+    }
+    return impl_params.every((p,idx) => isTypeAssignable(method_params[idx].type, p.type))
+        && isTypeAssignable(method.returnType, impl.returnType);
+}
+
 /**
  * @param {SourceType} source_type 
  * @param {*} probs 
@@ -44,7 +60,10 @@ function checkImplementedInterfaces(source_type, probs) {
             }
             const namedsig = `${m.name}${m.methodSignature}`
             if (implemented.indexOf(namedsig) < 0) {
-                missing_methods.push(nonAbstractLabel(m.label));
+                // perform a more detailed search for a compatible match
+                if (!source_type.methods.find(source_method => source_method.name === m.name && isMethodCompatible(source_method, m))) {
+                    missing_methods.push(nonAbstractLabel(m.label));
+                }
             }
         })
         if (missing_methods.length) {