diff --git a/langkit/generic_interface.py b/langkit/generic_interface.py
index 43df650e5..6650afbda 100644
--- a/langkit/generic_interface.py
+++ b/langkit/generic_interface.py
@@ -287,7 +287,8 @@ def find_implementations_of_method(
         )
         for m in class_members:
             if (
-                m.original_name not in implementations
+                not m.is_internal
+                and m.original_name not in implementations
                 and m.implements == method
             ):
                 implementations[m.original_name] = m
diff --git a/testsuite/tests/generic_interfaces/env_spec/foo.lkt b/testsuite/tests/generic_interfaces/env_spec/foo.lkt
new file mode 100644
index 000000000..18e8fadc5
--- /dev/null
+++ b/testsuite/tests/generic_interfaces/env_spec/foo.lkt
@@ -0,0 +1,25 @@
+# Defining an env spec in a class implementing an interface used to cause a
+# compilation error.
+
+import lexer_example
+
+grammar foo_grammar {
+    @main_rule main_rule <- BarNode("example")
+}
+
+@generic_interface()
+trait Interface {
+    fun method(): Bool
+}
+
+class FooNode implements Node[FooNode] {
+}
+
+class BarNode: FooNode implements Interface {
+    @exported
+    fun prop(): Bool implements Interface.method = true
+
+    env_spec {
+        add_env()
+    }
+}
diff --git a/testsuite/tests/generic_interfaces/env_spec/test.out b/testsuite/tests/generic_interfaces/env_spec/test.out
new file mode 100644
index 000000000..447c956ad
--- /dev/null
+++ b/testsuite/tests/generic_interfaces/env_spec/test.out
@@ -0,0 +1,4 @@
+== foo.lkt ==
+Code generation was successful
+
+lkt_compile: Done
diff --git a/testsuite/tests/generic_interfaces/env_spec/test.yaml b/testsuite/tests/generic_interfaces/env_spec/test.yaml
new file mode 100644
index 000000000..4a499fbd3
--- /dev/null
+++ b/testsuite/tests/generic_interfaces/env_spec/test.yaml
@@ -0,0 +1 @@
+driver: lkt_compile