diff --git a/pvlib/pvsystem.py b/pvlib/pvsystem.py
index 9ef49dd6d7..585a82c916 100644
--- a/pvlib/pvsystem.py
+++ b/pvlib/pvsystem.py
@@ -1678,7 +1678,7 @@ def sapm(effective_irradiance, temp_cell, module):
     irrad_ref = 1000
     # TODO: remove this warning in v0.8 after deprecation period for change in
     # effective irradiance units, made in v0.7
-    if np.all(effective_irradiance) < 2.0:
+    if np.all(effective_irradiance < 2.0):
         import warnings
         warnings.warn('effective_irradiance inputs appear to be in suns.'
                       ' Units changed in v0.7 from suns to W/m2',