diff --git a/frege-interpreter-core/src/main/frege/frege/interpreter/FregeInterpreter.fr b/frege-interpreter-core/src/main/frege/frege/interpreter/FregeInterpreter.fr
index d67231f..d432dc3 100644
--- a/frege-interpreter-core/src/main/frege/frege/interpreter/FregeInterpreter.fr
+++ b/frege-interpreter-core/src/main/frege/frege/interpreter/FregeInterpreter.fr
@@ -290,11 +290,9 @@ symbolClass symbol g = g.unpack symbol.name.getpack
  * until one of them returns an error
  -}
 run src predefs steps = do
-    g <- getST
-    let scriptType = findScriptType src
+    let scriptType = findSourceType src predefs
         varName = findUnusedVariableName (predefs ++ src)
         source = buildScript src scriptType predefs "Console" varName
-    changeST $ const g
     changeST Global.{gen <- GenSt.{printer=IO.stdout}}    -- just to have no undefined value there
     foreach (steps source) runpass
     g <- getST
@@ -306,6 +304,35 @@ run src predefs steps = do
                   sym = fst $ StG.run (resolveSymbol varName) g
       else return Nothing
 
+findSourceType :: String -> String -> SourceType
+findSourceType src predefs =
+  case calcSourceType src of
+    Just ModuleSource -> SourceType.ModuleSource
+    Just ExpressionSource -> SourceType.ExpressionSource
+    otherwise -> case calcSourceType (buildScript src SourceType.DefinitionsSource predefs "T" "") of
+                   Just ModuleSource -> SourceType.DefinitionsSource
+                   _ -> SourceType.ExpressionSource
+  where
+    calcSourceType src = fst $ StG.run (calculateSourceTypeST src) env
+    env = interpreterCompilerEnv InterpreterClassLoader.default
+
+calculateSourceTypeST :: String -> StG (Maybe SourceType)
+calculateSourceTypeST src = do
+    g       <- getST
+    pw <- doio $ StringWriter.new () >>= StringWriter.printer
+    changeST Global.{sub <- SubSt.{stderr=pw}}
+    runpass (lexPass src, "lexical analysis                      ", postTrue)
+    g <- getST
+    if g.errors != 0
+      then return Nothing
+      else do
+        let tokens = filter noDocComment g.sub.toks.toList
+        result <- Parse.pass tokens
+        case result of
+          Nothing -> return Nothing
+          Just (GUtil.Program.Module _) -> return (Just SourceType.ModuleSource)
+          _ -> return (Just SourceType.ExpressionSource)
+
 {-
 Compiler state with interpreter options
 There is no IO; The classes are loaded in memory.
@@ -371,27 +398,6 @@ instance Show SourceInfo where
   show (Expression _) = "Expression"
   show (Definitions _) = "Definitions"
 
-findScriptType :: String -> SourceType
-findScriptType src = fst $ StG.run f (interpreterCompilerEnv InterpreterClassLoader.default) where
-  f = do
-    runpass (lexPass src,         "lexical analysis                      ", postTrue)
-    g <- getST
-    if g.errors == 0
-      then scriptTypePass src
-      else return SourceType.ModuleSource
-
-scriptTypePass src = do
-  g <- getST
-  let tokens = filter noDocComment g.sub.toks.toList
-  case tokens of
-    [] -> return SourceType.ModuleSource
-    (Token{tokid=PACKAGE}) : _ -> return SourceType.ModuleSource
-    _ -> do
-      isDef <- isDefinition src
-      if isDef
-        then return SourceType.DefinitionsSource
-        else return SourceType.ExpressionSource
-
 noDocComment Token{tokid} = tokid != COMMENT && tokid != DOCUMENTATION
 
 moduleDeclScript moduleName = "module " ++ moduleName ++ " where"
@@ -571,23 +577,6 @@ iparsePass f = do
 indent n src = (unlines . map (spaces ++) . lines $ src) where
   spaces = concat $ replicate n " "
 
-isDefinition :: String -> StG Bool
-isDefinition src = do
-    g       <- getST
-    sw <- doio $ StringWriter.new ()
-    pw <- doio $ sw.printer
-    let modDecl = intercalate newLine ["module T where", src]
-    changeST Global.{sub <- SubSt.{stderr=pw}}
-    runpass (lexPass modDecl, "lexical analysis                      ", postTrue)
-    g <- getST
-    if g.errors != 0
-      then return false
-      else do
-        let tokens = filter noDocComment g.sub.toks.toList
-        result <- Parse.pass tokens
-        g <- getST
-        return $ g.errors == 0
-
 lexPass src = do
     changeST Global.{sub <- SubSt.{toks = arrayFromList []}
                             . SubSt.{definitions = []}
diff --git a/frege-script-engine/src/test/java/frege/scriptengine/FregeScriptEngineTest.java b/frege-script-engine/src/test/java/frege/scriptengine/FregeScriptEngineTest.java
index 648dbce..09e3a8b 100644
--- a/frege-script-engine/src/test/java/frege/scriptengine/FregeScriptEngineTest.java
+++ b/frege-script-engine/src/test/java/frege/scriptengine/FregeScriptEngineTest.java
@@ -7,7 +7,11 @@
 import javax.script.ScriptException;
 
 import org.junit.Before;
+import org.junit.Rule;
 import org.junit.Test;
+import org.junit.rules.TestRule;
+import org.junit.rules.TestWatcher;
+import org.junit.runner.Description;
 
 import java.math.BigInteger;
 
@@ -93,4 +97,29 @@ public void testUnpackagedModule() throws ScriptException {
         final Object expected = "I am bar";
         assertEquals(expected, actual);
     }
+
+    @Test
+    public void testOperators() throws ScriptException {
+        frege.eval("infix 1 `³`");
+        frege.eval("(x³) = x^3");
+        final Object expected = frege.eval("(2³)");
+        final Object actual = 8;
+        assertEquals(expected, actual);
+    }
+
+    @Test
+    public void testImportOperators() throws ScriptException {
+        frege.eval("import Data.Monoid");
+        frege.eval("import frege.data.wrapper.Num");
+        final Object expected = frege.eval("Sum.unwrap $ Sum 1 <> Sum 0");
+        final Object actual = 1;
+        assertEquals(expected, actual);
+    }
+
+    @Test
+    public void testTypeAnnotation() throws ScriptException {
+        final Object expected = frege.eval("(one :: Int)");
+        final Object actual = 1;
+        assertEquals(expected, actual);
+    }
 }
diff --git a/pom.xml b/pom.xml
index e13add7..300a5de 100644
--- a/pom.xml
+++ b/pom.xml
@@ -98,7 +98,7 @@
     <dependency>
       <groupId>junit</groupId>
       <artifactId>junit</artifactId>
-      <version>3.8.1</version>
+      <version>4.12</version>
       <scope>test</scope>
     </dependency>
   </dependencies>