diff --git a/interpreter.py b/interpreter.py
index 941d6bd95..cfd820171 100644
--- a/interpreter.py
+++ b/interpreter.py
@@ -1589,17 +1589,23 @@ class Interpreter():
     def evaluate_arithmeticstatement(self, cur):
         l = self.to_native(self.evaluate_statement(cur.left))
         r = self.to_native(self.evaluate_statement(cur.right))
-        if isinstance(l, str) or isinstance(r, str):
-            l = str(l)
-            r = str(r)
 
         if cur.operation == 'add':
-            return l + r
+            try:
+                return l + r
+            except Exception as e:
+                raise InvalidCode('Invalid use of addition: ' + str(e))
         elif cur.operation == 'sub':
+            if not isinstance(l, int) or not isinstance(r, int):
+                raise InvalidCode('Subtraction works only with integers.')
             return l - r
         elif cur.operation == 'mul':
+            if not isinstance(l, int) or not isinstance(r, int):
+                raise InvalidCode('Multiplication works only with integers.')
             return l * r
         elif cur.operation == 'div':
+            if not isinstance(l, int) or not isinstance(r, int):
+                raise InvalidCode('Division works only with integers.')
             return l // r
         else:
             raise InvalidCode('You broke me.')
diff --git a/test cases/failing/11 object arithmetic/meson.build b/test cases/failing/11 object arithmetic/meson.build
index 34e3a7a5e..9a7a6565c 100644
--- a/test cases/failing/11 object arithmetic/meson.build	
+++ b/test cases/failing/11 object arithmetic/meson.build	
@@ -1,3 +1,3 @@
-project('object arithmetic')
+project('object arithmetic', 'c')
 
 foo = '5' + meson
diff --git a/test cases/failing/12 string arithmetic/meson.build b/test cases/failing/12 string arithmetic/meson.build
index 753f62b25..c02a865a4 100644
--- a/test cases/failing/12 string arithmetic/meson.build	
+++ b/test cases/failing/12 string arithmetic/meson.build	
@@ -1,3 +1,3 @@
-project('string arithmetic')
+project('string arithmetic', 'c')
 
-foo = 'a' / 'b'
+foo = 'a' + 3
diff --git a/test cases/failing/13 array arithmetic/meson.build b/test cases/failing/13 array arithmetic/meson.build
index ceaa8bc08..3ddf06092 100644
--- a/test cases/failing/13 array arithmetic/meson.build	
+++ b/test cases/failing/13 array arithmetic/meson.build	
@@ -1,3 +1,3 @@
-project('array arithmetic')
+project('array arithmetic', 'c')
 
-foo = ['a', 'b'] * ['6', '4']
+foo = ['a', 'b'] * 3