diff --git a/README.md b/README.md
index 720f36c..11d81b3 100644
--- a/README.md
+++ b/README.md
@@ -88,7 +88,7 @@ Import as a Gradle dependency:
 
 ```groovy
 dependencies {
-    implementation("io.github.over-run:marshal:0.1.0-alpha.31-jdk23")
+    implementation("io.github.over-run:marshal:0.1.0-alpha.32-jdk23")
 }
 ```
 
diff --git a/gradle.properties b/gradle.properties
index 98c0864..ad8e9eb 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -12,7 +12,7 @@ projGroupId=io.github.over-run
 projArtifactId=marshal
 # The project name should only contain lowercase letters, numbers and hyphen.
 projName=marshal
-projVersion=0.1.0-alpha.31-jdk23
+projVersion=0.1.0-alpha.32-jdk23
 projDesc=Marshaler of native libraries
 # Uncomment them if you want to publish to maven repository.
 projUrl=https://github.com/Over-Run/marshal
diff --git a/src/main/java/overrun/marshal/Downcall.java b/src/main/java/overrun/marshal/Downcall.java
index 192a036..c0d402c 100644
--- a/src/main/java/overrun/marshal/Downcall.java
+++ b/src/main/java/overrun/marshal/Downcall.java
@@ -647,29 +647,31 @@ private static DowncallData generateData(
             }
             descriptorMap1.put(entrypoint, descriptor);
 
-            final Optional<MemorySegment> optional = lookup.find(entrypoint);
-            MethodHandle handle;
-            if (optional.isPresent()) {
-                // linker options
-                final Linker.Option[] options;
-                final Critical critical = method.getDeclaredAnnotation(Critical.class);
-                if (critical != null) {
-                    options = critical.allowHeapAccess() ? OPTION_CRITICAL_TRUE : OPTION_CRITICAL_FALSE;
-                } else {
-                    options = NO_OPTION;
-                }
+            if (descriptor != null) {
+                final Optional<MemorySegment> optional = lookup.find(entrypoint);
+                MethodHandle handle;
+                if (optional.isPresent()) {
+                    // linker options
+                    final Linker.Option[] options;
+                    final Critical critical = method.getDeclaredAnnotation(Critical.class);
+                    if (critical != null) {
+                        options = critical.allowHeapAccess() ? OPTION_CRITICAL_TRUE : OPTION_CRITICAL_FALSE;
+                    } else {
+                        options = NO_OPTION;
+                    }
 
-                handle = transform.apply(LINKER.downcallHandle(optional.get(), descriptor, options));
-            } else {
-                MethodHandle apply = transform.apply(null);
-                if (apply != null || method.isDefault()) {
-                    handle = apply;
+                    handle = transform.apply(LINKER.downcallHandle(optional.get(), descriptor, options));
                 } else {
-                    throw new NoSuchElementException("Symbol not found: " + entrypoint + " (" + descriptor + "): " + methodData.signatureString());
+                    MethodHandle apply = transform.apply(null);
+                    if (apply != null || method.isDefault()) {
+                        handle = apply;
+                    } else {
+                        throw new NoSuchElementException("Symbol not found: " + entrypoint + " (" + descriptor + "): " + methodData.signatureString());
+                    }
+                }
+                if (!map.containsKey(entrypoint) || map.get(entrypoint) == null) {
+                    map.putIfAbsent(entrypoint, handle);
                 }
-            }
-            if (!map.containsKey(entrypoint) || map.get(entrypoint) == null) {
-                map.put(entrypoint, handle);
             }
         }
         return new DowncallData(Collections.unmodifiableMap(descriptorMap1),
diff --git a/src/test/java/overrun/marshal/test/downcall/IDowncall.java b/src/test/java/overrun/marshal/test/downcall/IDowncall.java
index 1e41182..17d60e4 100644
--- a/src/test/java/overrun/marshal/test/downcall/IDowncall.java
+++ b/src/test/java/overrun/marshal/test/downcall/IDowncall.java
@@ -38,10 +38,7 @@
  * @since 0.1.0
  */
 public interface IDowncall {
-    Map<String, FunctionDescriptor> MAP = Map.of(
-        "testDefault", FunctionDescriptor.of(ValueLayout.JAVA_INT),
-        "testReturnInt", FunctionDescriptor.of(ValueLayout.JAVA_INT)
-    );
+    Map<String, FunctionDescriptor> MAP = Map.of("testDefault", FunctionDescriptor.of(ValueLayout.JAVA_INT));
 
     static IDowncall getInstance(boolean testDefaultNull) {
         ProcessorTypes.registerStruct(Vector3.class, Vector3.OF);