diff --git a/adafruit_ccs811.py b/adafruit_ccs811.py
index 7cc10dc..40932a7 100644
--- a/adafruit_ccs811.py
+++ b/adafruit_ccs811.py
@@ -138,7 +138,7 @@ def __init__(self, i2c_bus, address=0x5A):
         # make sure there are no errors and we have entered application mode
         if self.error:
             raise RuntimeError(
-                "Device returned a error! Try removing and reapplying power to "
+                "Device returned an error! Try removing and reapplying power to "
                 "the device and running the code again."
             )
         if not self.fw_mode: