diff --git a/hw/qdev-properties.c b/hw/qdev-properties.c
index 9219cd7..96d814c 100644
--- a/hw/qdev-properties.c
+++ b/hw/qdev-properties.c
@@ -514,6 +514,8 @@ static int parse_pci_devfn(DeviceState *dev, Property *prop, const char *str)
             return -EINVAL;
         }
     }
+    if (slot > MAX_PCI_SLOTS)
+        return -EINVAL;
     if (str[n] != '\0')
         return -EINVAL;
     if (fn > 7)
diff --git a/hw/qdev.h b/hw/qdev.h
index 678f8b7..fcfe52e 100644
--- a/hw/qdev.h
+++ b/hw/qdev.h
@@ -7,6 +7,9 @@
 #include "qemu-char.h"
 #include "qemu-option.h"
 
+
+#define MAX_PCI_SLOTS 0x1f
+
 typedef struct Property Property;
 
 typedef struct PropertyInfo PropertyInfo;