diff --git a/jso/impl/src/main/java/org/teavm/jso/impl/JSClassProcessor.java b/jso/impl/src/main/java/org/teavm/jso/impl/JSClassProcessor.java
index d36d3d3a6..222de5406 100644
--- a/jso/impl/src/main/java/org/teavm/jso/impl/JSClassProcessor.java
+++ b/jso/impl/src/main/java/org/teavm/jso/impl/JSClassProcessor.java
@@ -337,7 +337,7 @@ class JSClassProcessor {
         if (invoke.getInstance() != null) {
             if (!typeHelper.isSupportedType(ValueType.object(method.getOwnerName()))) {
                 diagnostics.error(callLocation, "Method {{m0}} is not a proper native JavaScript method "
-                        + " declaration. It is non-static and declared on a non-overlay class {{c1}}",
+                        + "declaration. It is non-static and declared on a non-overlay class {{c1}}",
                         invoke.getMethod(), method.getOwnerName());
                 valid = false;
             }
@@ -443,7 +443,7 @@ class JSClassProcessor {
     private boolean validateSignature(MethodReader method, CallLocation callLocation, boolean[] byRefParams) {
         if (method.getResultType() != ValueType.VOID && !typeHelper.isSupportedType(method.getResultType())) {
             diagnostics.error(callLocation, "Method {{m0}} is not a proper native JavaScript method "
-                    + "declaration", method.getReference());
+                    + "declaration, since it returns wrong type", method.getReference());
             return false;
         }
 
@@ -453,13 +453,13 @@ class JSClassProcessor {
             ValueType paramType = parameterTypes[i];
             if (!typeHelper.isSupportedType(paramType)) {
                 diagnostics.error(callLocation, "Method {{m0}} is not a proper native JavaScript method "
-                        + "declaration: its " + (i + 1) + "th argument has wrong type", method.getReference());
+                        + "declaration: its " + (i + 1) + "th parameter has wrong type", method.getReference());
                 return false;
             }
             if (parameterAnnotations[i].get(JSByRef.class.getName()) != null) {
                 if (!typeHelper.isSupportedByRefType(paramType)) {
                     diagnostics.error(callLocation, "Method {{m0}} is not a proper native JavaScript method "
-                            + "declaration: its " + (i + 1) + "th argument is declared as JSByRef, "
+                            + "declaration: its " + (i + 1) + "th parameter is declared as JSByRef, "
                             + "which has incompatible type", method.getReference());
                     return false;
                 }
diff --git a/tests/src/test/java/org/teavm/tests/JSOTest.java b/tests/src/test/java/org/teavm/tests/JSOTest.java
index 277310b8e..ff5fd6d94 100644
--- a/tests/src/test/java/org/teavm/tests/JSOTest.java
+++ b/tests/src/test/java/org/teavm/tests/JSOTest.java
@@ -35,14 +35,13 @@ public class JSOTest {
         Problem foundProblem = build("callJSBodyWithWrongParameter").stream().filter(problem -> {
             return problem.getLocation().getMethod().getName().equals("callJSBodyWithWrongParameter")
                     && problem.getText().equals("Method {{m0}} is not a proper native JavaScript method "
-                        + " declaration. Its parameter #1 has invalid type {{t1}}");
+                        + "declaration: its 1th parameter has wrong type");
         }).findAny().orElse(null);
 
         assertNotNull(foundProblem);
         Object[] params = foundProblem.getParams();
         assertThat(params[0], is(new MethodReference(JSOTest.class, "jsBodyWithWrongParameter",
                 Object.class, void.class)));
-        assertThat(params[1], is(ValueType.parse(Object.class)));
     }
 
     private static void callJSBodyWithWrongParameter() {
@@ -57,7 +56,7 @@ public class JSOTest {
         Problem foundProblem = build("callWrongNonStaticJSBody").stream().filter(problem -> {
             return problem.getLocation().getMethod().getName().equals("callWrongNonStaticJSBody")
                     && problem.getText().equals("Method {{m0}} is not a proper native JavaScript method "
-                        + " declaration. It is non-static and declared on a non-overlay class {{c1}}");
+                        + "declaration. It is non-static and declared on a non-overlay class {{c1}}");
         }).findAny().orElse(null);
 
         assertNotNull(foundProblem);
@@ -78,14 +77,13 @@ public class JSOTest {
         Problem foundProblem = build("callJSBodyWithWrongReturningType").stream().filter(problem -> {
             return problem.getLocation().getMethod().getName().equals("callJSBodyWithWrongReturningType")
                     && problem.getText().equals("Method {{m0}} is not a proper native JavaScript method "
-                            + " declaration, since it returns invalid type {{t1}}");
+                            + "declaration, since it returns wrong type");
         }).findAny().orElse(null);
 
         assertNotNull(foundProblem);
         Object[] params = foundProblem.getParams();
         assertThat(params[0], is(new MethodReference(JSOTest.class, "jsBodyWithWrongReturningType", String.class,
                 Object.class)));
-        assertThat(params[1], is(ValueType.parse(Object.class)));
     }
 
     private static void callJSBodyWithWrongReturningType() {