diff --git a/core/src/main/java/org/teavm/backend/javascript/JavaScriptTarget.java b/core/src/main/java/org/teavm/backend/javascript/JavaScriptTarget.java
index 67f894372..3583a0304 100644
--- a/core/src/main/java/org/teavm/backend/javascript/JavaScriptTarget.java
+++ b/core/src/main/java/org/teavm/backend/javascript/JavaScriptTarget.java
@@ -326,6 +326,11 @@ public class JavaScriptTarget implements TeaVMTarget, TeaVMJavaScriptHost {
 
         Program program = new Program();
         method.setProgram(program);
+
+        for (int i = 0; i <= method.parameterCount(); ++i) {
+            program.createVariable();
+        }
+
         BasicBlock block = program.createBasicBlock();
         Variable exceptionVar = program.createVariable();
         ConstructInstruction newExceptionInsn = new ConstructInstruction();
diff --git a/core/src/main/java/org/teavm/model/optimization/UnusedVariableElimination.java b/core/src/main/java/org/teavm/model/optimization/UnusedVariableElimination.java
index 4a23d50b0..d3b54def2 100644
--- a/core/src/main/java/org/teavm/model/optimization/UnusedVariableElimination.java
+++ b/core/src/main/java/org/teavm/model/optimization/UnusedVariableElimination.java
@@ -29,6 +29,10 @@ public class UnusedVariableElimination implements MethodOptimization {
         boolean[] escaping = VariableEscapeAnalyzer.findEscapingVariables(program);
         boolean[] used = new boolean[escaping.length];
 
+        for (int i = 0; i <= method.parameterCount(); ++i) {
+            used[i] = true;
+        }
+
         int[] stack = new int[graph.size() * 2];
         int top = 0;
         for (int i = 0; i < used.length; ++i) {
diff --git a/core/src/main/java/org/teavm/model/util/TypeInferer.java b/core/src/main/java/org/teavm/model/util/TypeInferer.java
index e617bff93..36db9b292 100644
--- a/core/src/main/java/org/teavm/model/util/TypeInferer.java
+++ b/core/src/main/java/org/teavm/model/util/TypeInferer.java
@@ -28,7 +28,7 @@ public class TypeInferer {
     GraphBuilder arrayElemBuilder;
 
     public void inferTypes(ProgramReader program, MethodReference method) {
-        int sz = Math.max(method.parameterCount(), program.variableCount());
+        int sz = program.variableCount();
         types = new VariableType[sz];
 
         types[0] = VariableType.OBJECT;