diff --git a/core/src/main/java/org/teavm/backend/javascript/rendering/RuntimeRenderer.java b/core/src/main/java/org/teavm/backend/javascript/rendering/RuntimeRenderer.java
index e2613aee8..3f3a0d5fe 100644
--- a/core/src/main/java/org/teavm/backend/javascript/rendering/RuntimeRenderer.java
+++ b/core/src/main/java/org/teavm/backend/javascript/rendering/RuntimeRenderer.java
@@ -180,7 +180,7 @@ public class RuntimeRenderer {
             return false;
         }
         MethodReader method = cls.getMethod(STRING_INTERN_METHOD);
-        return method != null && method.getProgram() != null;
+        return method != null && method.hasModifier(ElementModifier.NATIVE);
     }
 
     private void renderRuntimeObjcls() throws IOException {
diff --git a/core/src/main/java/org/teavm/model/PreOptimizingClassHolderSource.java b/core/src/main/java/org/teavm/model/PreOptimizingClassHolderSource.java
index 0cbca685c..6b0852601 100644
--- a/core/src/main/java/org/teavm/model/PreOptimizingClassHolderSource.java
+++ b/core/src/main/java/org/teavm/model/PreOptimizingClassHolderSource.java
@@ -49,8 +49,10 @@ public class PreOptimizingClassHolderSource implements ClassHolderSource {
             return cls;
         }
         for (MethodHolder method : cls.getMethods()) {
-            new GlobalValueNumbering(true).optimize(method.getProgram());
-            new UnusedVariableElimination().optimize(method, method.getProgram());
+            if (method.getProgram() != null) {
+                new GlobalValueNumbering(true).optimize(method.getProgram());
+                new UnusedVariableElimination().optimize(method, method.getProgram());
+            }
         }
         return cls;
     }
diff --git a/core/src/main/java/org/teavm/parsing/ClassRefsRenamer.java b/core/src/main/java/org/teavm/parsing/ClassRefsRenamer.java
index 6d5b6d1b1..40a079964 100644
--- a/core/src/main/java/org/teavm/parsing/ClassRefsRenamer.java
+++ b/core/src/main/java/org/teavm/parsing/ClassRefsRenamer.java
@@ -129,7 +129,9 @@ public class ClassRefsRenamer extends AbstractInstructionVisitor {
         renamedMethod.setLevel(method.getLevel());
         renamedMethod.setProgram(method.getProgram());
         rename(method.getAnnotations(), renamedMethod.getAnnotations());
-        rename(renamedMethod.getProgram());
+        if (renamedMethod.getProgram() != null) {
+            rename(renamedMethod.getProgram());
+        }
 
         renamedMethod.setTypeParameters(rename(method.getTypeParameters()));
         GenericValueType genericResultType = method.getGenericResultType();
diff --git a/core/src/main/java/org/teavm/parsing/Parser.java b/core/src/main/java/org/teavm/parsing/Parser.java
index 527b96c0d..a2d7b6218 100644
--- a/core/src/main/java/org/teavm/parsing/Parser.java
+++ b/core/src/main/java/org/teavm/parsing/Parser.java
@@ -79,23 +79,27 @@ public class Parser {
         ValueType[] signature = MethodDescriptor.parseSignature(node.desc);
         MethodHolder method = new MethodHolder(referenceCache.getCached(new MethodDescriptor(node.name, signature)));
         parseModifiers(node.access, method, DECL_METHOD);
-
-        ProgramParser programParser = new ProgramParser(referenceCache);
-        programParser.setFileName(fileName);
-        Program program = programParser.parse(node);
-        new UnreachableBasicBlockEliminator().optimize(program);
-        PhiUpdater phiUpdater = new PhiUpdater();
-        Variable[] argumentMapping = applySignature(program, method.getParameterTypes());
-        phiUpdater.updatePhis(program, argumentMapping);
-        method.setProgram(program);
-        applyDebugNames(program, phiUpdater, programParser, argumentMapping);
-
         parseAnnotations(method.getAnnotations(), node.visibleAnnotations, node.invisibleAnnotations);
-        applyDebugNames(program, phiUpdater, programParser,
-                applySignature(program, method.getDescriptor().getParameterTypes()));
-        while (program.variableCount() <= method.parameterCount()) {
-            program.createVariable();
+
+        if (node.instructions.size() > 0) {
+            ProgramParser programParser = new ProgramParser(referenceCache);
+            programParser.setFileName(fileName);
+            Program program = programParser.parse(node);
+            new UnreachableBasicBlockEliminator().optimize(program);
+            PhiUpdater phiUpdater = new PhiUpdater();
+            Variable[] argumentMapping = applySignature(program, method.getParameterTypes());
+            phiUpdater.updatePhis(program, argumentMapping);
+            method.setProgram(program);
+            applyDebugNames(program, phiUpdater, programParser, argumentMapping);
+
+            applyDebugNames(program, phiUpdater, programParser,
+                    applySignature(program, method.getDescriptor().getParameterTypes()));
+
+            while (program.variableCount() <= method.parameterCount()) {
+                program.createVariable();
+            }
         }
+
         if (node.annotationDefault != null) {
             method.setAnnotationDefault(parseAnnotationValue(node.annotationDefault));
         }