diff --git a/lib/ansible/inventory/script.py b/lib/ansible/inventory/script.py
index 8b2e4619a9..e43cf24972 100644
--- a/lib/ansible/inventory/script.py
+++ b/lib/ansible/inventory/script.py
@@ -84,10 +84,14 @@ class InventoryScript(object):
 
             if not isinstance(data, dict):
                 data = {'hosts': data}
+            # is not those subkeys, then simplified syntax, host with vars
             elif not any(k in data for k in ('hosts','vars')):
                 data = {'hosts': [group_name], 'vars': data}
 
             if 'hosts' in data:
+                if not isinstance(data['hosts'], list):
+                    raise errors.AnsibleError("You defined a group \"%s\" with bad "
+                        "data for the host list:\n %s" % (group_name, data))
 
                 for hostname in data['hosts']:
                     if not hostname in all_hosts:
@@ -96,6 +100,10 @@ class InventoryScript(object):
                     group.add_host(host)
 
             if 'vars' in data:
+                if not isinstance(data['vars'], dict):
+                    raise errors.AnsibleError("You defined a group \"%s\" with bad "
+                        "data for variables:\n %s" % (group_name, data))
+
                 for k, v in data['vars'].iteritems():
                     if group.name == all.name:
                         all.set_variable(k, v)
diff --git a/lib/ansible/utils/__init__.py b/lib/ansible/utils/__init__.py
index c18174b00d..1e6a5383c0 100644
--- a/lib/ansible/utils/__init__.py
+++ b/lib/ansible/utils/__init__.py
@@ -696,12 +696,23 @@ def parse_kv(args):
                 options[k.strip()] = unquote(v.strip())
     return options
 
+def _validate_both_dicts(a, b):
+
+    if not (isinstance(a, dict) and isinstance(b, dict)):
+        raise errors.AnsibleError(
+            "failed to combine variables, expected dicts but got a '%s' and a '%s'" % (type(a).__name__, type(b).__name__)
+        )
+
 def merge_hash(a, b):
     ''' recursively merges hash b into a
     keys from b take precedence over keys from a '''
 
     result = {}
 
+    # we check here as well as in combine_vars() since this
+    # function can work recursively with nested dicts
+    _validate_both_dicts(a, b)
+
     for dicts in a, b:
         # next, iterate over b keys and values
         for k, v in dicts.iteritems():
@@ -1308,6 +1319,8 @@ def listify_lookup_plugin_terms(terms, basedir, inject):
 
 def combine_vars(a, b):
 
+    _validate_both_dicts(a, b)
+
     if C.DEFAULT_HASH_BEHAVIOUR == "merge":
         return merge_hash(a, b)
     else: