diff --git a/validators/validators.py b/validators/validators.py
index aadab3e..9ff8f47 100644
--- a/validators/validators.py
+++ b/validators/validators.py
@@ -11,6 +11,8 @@ def empty(field: str) -> bool:
 
 
 def iso_date(field: str) -> bool:
+    if not field:
+        return False
     try:
         datetime.datetime.strptime(field, "%Y-%m-%d")
         return True
@@ -19,6 +21,10 @@ def iso_date(field: str) -> bool:
 
 
 def valid_iban(field: str) -> bool:
+    if not field:
+        return False
+    if not type(field) == str:
+        return False
     try:
         IBAN(field)
         return True
@@ -27,6 +33,10 @@ def valid_iban(field: str) -> bool:
 
 
 def valid_bic(field: str) -> bool:
+    if not field:
+        return False
+    if not type(field) == str:
+        return False
     try:
         BIC(field)
         return True