diff --git a/src/main/java/io/usethesource/vallang/IWithKeywordParameters.java b/src/main/java/io/usethesource/vallang/IWithKeywordParameters.java
index 29c12e0c9..1dc772c5c 100644
--- a/src/main/java/io/usethesource/vallang/IWithKeywordParameters.java
+++ b/src/main/java/io/usethesource/vallang/IWithKeywordParameters.java
@@ -14,7 +14,7 @@
 
 import java.util.Map;
 import java.util.Set;
-
+import org.checkerframework.checker.nullness.qual.Nullable;
 import io.usethesource.vallang.exceptions.FactTypeUseException;
 
 public interface IWithKeywordParameters<T extends IValue> {
@@ -25,7 +25,7 @@ public interface IWithKeywordParameters<T extends IValue> {
 	 * @param label identifies the parameter
 	 * @return a value if the parameter has a value on this node or null otherwise
 	 */
-	public IValue getParameter(String label);
+	public @Nullable IValue getParameter(String label);
 	
 	/**
 	 * Set the value of an parameter
diff --git a/src/main/java/io/usethesource/vallang/impl/fields/AbstractDefaultWithKeywordParameters.java b/src/main/java/io/usethesource/vallang/impl/fields/AbstractDefaultWithKeywordParameters.java
index 0ad3ff308..210f0c308 100644
--- a/src/main/java/io/usethesource/vallang/impl/fields/AbstractDefaultWithKeywordParameters.java
+++ b/src/main/java/io/usethesource/vallang/impl/fields/AbstractDefaultWithKeywordParameters.java
@@ -66,7 +66,7 @@ public String toString() {
 	}
 
 	@Override
-	public IValue getParameter(String label) {
+	public @Nullable IValue getParameter(String label) {
 		return parameters.get(label);
 	}
 
@@ -139,7 +139,7 @@ public boolean equals(@Nullable Object other) {
 
 		// TODO: there should be a faster way for this
 		for (String key : parameters.keySet()) {
-			if (!getParameter(key).equals(o.getParameter(key))) {
+			if (!parameters.get(key).equals(o.getParameter(key))) {
 				return false;
 			}
 		}
diff --git a/src/test/java/io/usethesource/vallang/ValueProvider.java b/src/test/java/io/usethesource/vallang/ValueProvider.java
index 56f9a7562..fa556058a 100644
--- a/src/test/java/io/usethesource/vallang/ValueProvider.java
+++ b/src/test/java/io/usethesource/vallang/ValueProvider.java
@@ -7,6 +7,7 @@
 import java.util.Collection;
 import java.util.HashMap;
 import java.util.Map;
+import java.util.Objects;
 import java.util.Random;
 import java.util.function.BiFunction;
 import java.util.stream.Collectors;
@@ -259,15 +260,16 @@ private static long hashSeed(String string) {
      * @param cls       the class type of the parameter to generate an input for
      * @return a random object which is assignable to cls
      */
-    private Object argument(IValueFactory vf, TypeStore ts, Class<?> cls, ExpectedType expected, GivenValue givenValue, TypeConfig typeConfig, int depth, int width)  {
+    private Object argument(IValueFactory vf, TypeStore ts, Class<?> cls, @Nullable ExpectedType expected, GivenValue givenValue, TypeConfig typeConfig, int depth, int width)  {
         if (givenValue != null) {
             try {
                 if (expected != null) {
-                    return new StandardTextReader().read(vf, ts, readType(ts, expected), new StringReader(givenValue.value()));
-                }
-                else {
-                    return new StandardTextReader().read(vf, new StringReader(givenValue.value()));
+                    Type type = readType(ts, expected);
+                    if (type != null) {
+                        return new StandardTextReader().read(vf, ts, type, new StringReader(givenValue.value()));
+                    }
                 }
+                return new StandardTextReader().read(vf, new StringReader(givenValue.value()));
             } catch (FactTypeUseException | IOException e) {
                 System.err.println("[WARNING] failed to parse given value: " + givenValue.value());
             }
@@ -281,12 +283,13 @@ else if (cls.isAssignableFrom(TypeStore.class)) {
         }
         else if (cls.isAssignableFrom(Type.class)) {
             if (expected != null) {
-                return readType(ts, expected);
-            }
-            else {
-                RandomTypesConfig rtc = configureRandomTypes(typeConfig, depth);
-                return TypeFactory.getInstance().randomType(ts, rtc);
+                Type result = readType(ts, expected);
+                if (result != null) {
+                    return result;
+                }
             }
+            RandomTypesConfig rtc = configureRandomTypes(typeConfig, depth);
+            return TypeFactory.getInstance().randomType(ts, rtc);
         }
         else if (cls.isAssignableFrom(TypeFactory.class)) {
             return TypeFactory.getInstance();
@@ -336,7 +339,7 @@ private RandomTypesConfig configureRandomTypes(TypeConfig typeConfig, int depth)
      * @param noAnnotations 
      * @return an instance assignable to `cl`
      */
-    private IValue generateValue(IValueFactory vf, TypeStore ts, Class<? extends IValue> cl, ExpectedType expected, int depth, int width) {
+    private IValue generateValue(IValueFactory vf, TypeStore ts, Class<? extends IValue> cl, @Nullable ExpectedType expected, int depth, int width) {
         Type expectedType = tf.voidType();
 
         
@@ -345,8 +348,14 @@ private IValue generateValue(IValueFactory vf, TypeStore ts, Class<? extends IVa
         int i = 0;
         while (expectedType.isBottom() && i++ < 1000) {
             if (expected != null) {
-                expectedType = readType(ts, expected);
-                break;
+                Type read = readType(ts, expected);
+                if (read == null) {
+                    expected = null;
+                }
+                else {
+                    expectedType = read;
+                    break;
+                }
             }
             else {
                 expectedType = types
@@ -364,7 +373,7 @@ private IValue generateValue(IValueFactory vf, TypeStore ts, Class<? extends IVa
         return (previous = expectedType.randomValue(rnd, vf, ts, new HashMap<>(), depth, width));
     }
 
-    private static Type readType(TypeStore ts, ExpectedType expected) {
+    private static @Nullable Type readType(TypeStore ts, ExpectedType expected) {
         try {
             return tf.fromString(ts, new StringReader(expected.value()));
         } catch (IOException e) {