diff --git a/kiwi_scp/config.py b/kiwi_scp/config.py
index 44fc137..23c471e 100644
--- a/kiwi_scp/config.py
+++ b/kiwi_scp/config.py
@@ -48,7 +48,7 @@ class _Project(BaseModel):
 
     @root_validator(pre=True)
     @classmethod
-    def unify_project(cls, values):
+    def unify_project(cls, values) -> Dict[str, Any]:
         """parse different project notations"""
 
         if "name" in values:
@@ -91,7 +91,7 @@ class Config(BaseModel):
 
     version: constr(regex=RE_SEMVER) = "0.2.0"
 
-    shells: Optional[List[Path]] = [
+    shells: List[Path] = [
         Path("/bin/bash"),
     ]
 
@@ -152,9 +152,32 @@ class Config(BaseModel):
 
         return yml_string
 
+    @validator("shells", pre=True)
+    @classmethod
+    def unify_shells(cls, value) -> List[str]:
+        """parse different shells notations"""
+
+        if value is None:
+            return []
+
+        elif isinstance(value, list):
+            return value
+
+        elif isinstance(value, dict):
+            return list(value)
+
+        else:
+            # any other format (try to coerce to str first)
+            try:
+                return [str(value)]
+
+            except Exception as e:
+                # undefined format
+                raise ValueError("Invalid Shells Format")
+
     @validator("projects", pre=True)
     @classmethod
-    def unify_projects(cls, value):
+    def unify_projects(cls, value) -> List[Dict[str, str]]:
         """parse different projects notations"""
 
         if value is None:
@@ -173,8 +196,13 @@ class Config(BaseModel):
                         result.append(entry)
 
                     else:
-                        # handle single project name
-                        result.append({"name": str(entry)})
+                        try:
+                            # handle single project name
+                            result.append({"name": str(entry)})
+
+                        except Exception as e:
+                            # undefined format
+                            raise ValueError("Invalid Projects Format")
 
             return result
 
@@ -183,8 +211,14 @@ class Config(BaseModel):
             return [value]
 
         else:
-            # handle single project name
-            return [{"name": str(value)}]
+            # any other format (try to coerce to str first)
+            try:
+                # handle as a single project name
+                return [{"name": str(value)}]
+
+            except Exception as e:
+                # undefined format
+                raise ValueError("Invalid Projects Format")
 
     @validator("environment", pre=True)
     @classmethod
@@ -215,20 +249,20 @@ class Config(BaseModel):
 
             result: Dict[str, Optional[str]] = {}
             for item in value:
-                key, value = parse_str(str(item))
-                result[key] = value
+                try:
+                    key, value = parse_str(str(item))
+                    result[key] = value
+
+                except Exception as e:
+                    # undefined format
+                    raise ValueError("Invalid Environment Format")
 
             return result
 
-        elif isinstance(value, str):
-            # string format (single variable):
-            # "<var>=<value>"
-
-            key, value = parse_str(value)
-            return {key: value}
-
         else:
             # any other format (try to coerce to str first)
+            # string format (single variable):
+            # "<var>=<value>"
             try:
                 key, value = parse_str(str(value))
                 return {key: value}
diff --git a/tests/test_config.py b/tests/test_config.py
index 4571946..8acc3ec 100644
--- a/tests/test_config.py
+++ b/tests/test_config.py
@@ -8,6 +8,12 @@ from pydantic import ValidationError
 from kiwi_scp.config import Config
 
 
+class UnCoercible:
+    """A class that doesn't have a string representation"""
+    def __str__(self):
+        raise ValueError
+
+
 def test_default():
     c = Config()
     version = toml.load("./pyproject.toml")["tool"]["poetry"]["version"]
@@ -22,6 +28,70 @@ def test_default():
     assert c.network.cidr == IPv4Network("10.22.46.0/24")
 
 
+########
+# SHELLS
+########
+
+def test_shells_empty():
+    c = Config(shells=None)
+
+    assert c == Config(shells=[])
+
+    assert c.shells == []
+
+
+def test_shells_list():
+    c = Config(shells=["/bin/sh", "sh"])
+
+    assert len(c.shells) == 2
+    assert c.shells[0] == Path("/bin/sh")
+    assert c.shells[1] == Path("sh")
+
+    c = Config(shells=["/bin/bash"])
+
+    assert len(c.shells) == 1
+    assert c.shells[0] == Path("/bin/bash")
+
+
+def test_shells_dict():
+    c = Config(shells={"/bin/bash": None})
+
+    assert len(c.shells) == 1
+    assert c.shells[0] == Path("/bin/bash")
+
+
+def test_shells_coercible():
+    c = Config(shells="/bin/bash")
+
+    assert c == Config(shells=Path("/bin/bash"))
+
+    assert len(c.shells) == 1
+    assert c.shells[0] == Path("/bin/bash")
+
+    c = Config(shells=123)
+
+    assert len(c.shells) == 1
+    assert c.shells[0] == Path("123")
+
+
+def test_shells_uncoercible():
+    with pytest.raises(ValidationError) as exc_info:
+        Config(shells=UnCoercible())
+
+    assert len(exc_info.value.errors()) == 1
+    error = exc_info.value.errors()[0]
+    assert error["msg"] == "Invalid Shells Format"
+    assert error["type"] == "value_error"
+
+    with pytest.raises(ValidationError) as exc_info:
+        Config(shells=["/bin/bash", UnCoercible()])
+
+    assert len(exc_info.value.errors()) == 1
+    error = exc_info.value.errors()[0]
+    assert error["msg"] == "value is not a valid path"
+    assert error["type"] == "type_error.path"
+
+
 ##########
 # PROJECTS
 ##########
@@ -29,9 +99,7 @@ def test_default():
 def test_proj_empty():
     c = Config(projects=None)
 
-    assert c.projects == []
-
-    c = Config(projects=[])
+    assert c == Config(projects=[])
 
     assert c.projects == []
 
@@ -75,7 +143,7 @@ def test_proj_dict():
     assert p.override_storage is None
 
 
-def test_proj_name():
+def test_proj_coercible():
     c = Config(projects="project")
 
     assert c == Config(projects=["project"])
@@ -87,6 +155,24 @@ def test_proj_name():
     assert p.override_storage is None
 
 
+def test_proj_uncoercible():
+    with pytest.raises(ValidationError) as exc_info:
+        Config(projects=["valid", UnCoercible()])
+
+    assert len(exc_info.value.errors()) == 1
+    error = exc_info.value.errors()[0]
+    assert error["msg"] == "Invalid Projects Format"
+    assert error["type"] == "value_error"
+
+    with pytest.raises(ValidationError) as exc_info:
+        Config(projects=UnCoercible())
+
+    assert len(exc_info.value.errors()) == 1
+    error = exc_info.value.errors()[0]
+    assert error["msg"] == "Invalid Projects Format"
+    assert error["type"] == "value_error"
+
+
 #############
 # ENVIRONMENT
 #############
@@ -139,7 +225,7 @@ def test_env_list():
     assert c.environment["123"] is None
 
 
-def test_env_str():
+def test_env_coercible():
     c = Config(environment="variable=value")
 
     assert len(c.environment) == 1
@@ -152,8 +238,6 @@ def test_env_str():
     assert "variable" in c.environment
     assert c.environment["variable"] is None
 
-
-def test_env_coercible():
     c = Config(environment=123)
 
     assert len(c.environment) == 1
@@ -167,11 +251,7 @@ def test_env_coercible():
     assert c.environment["123.4"] is None
 
 
-def test_env_undef():
-    class UnCoercible:
-        def __str__(self):
-            raise ValueError
-
+def test_env_uncoercible():
     with pytest.raises(ValidationError) as exc_info:
         Config(environment=UnCoercible())
 
@@ -179,3 +259,11 @@ def test_env_undef():
     error = exc_info.value.errors()[0]
     assert error["msg"] == "Invalid Environment Format"
     assert error["type"] == "value_error"
+
+    with pytest.raises(ValidationError) as exc_info:
+        Config(environment=["valid", UnCoercible()])
+
+    assert len(exc_info.value.errors()) == 1
+    error = exc_info.value.errors()[0]
+    assert error["msg"] == "Invalid Environment Format"
+    assert error["type"] == "value_error"