diff --git a/src/hmf/cosmology/growth_factor.py b/src/hmf/cosmology/growth_factor.py
index ce72dcf..d418fb3 100644
--- a/src/hmf/cosmology/growth_factor.py
+++ b/src/hmf/cosmology/growth_factor.py
@@ -167,7 +167,8 @@ def growth_factor_fn(self, zmin=0.0, inverse=False):
 
     def growth_rate(self, z):
         """
-        Growth rate, dln(d)/dln(a) from Hamilton 2000 eq. 4.
+        Growth rate, dln(d)/dln(a) from Hamilton 2000 eq. 4
+        Note that the growth function g in Hamilton 2000 is defined as g=D*(1+z).
 
         Parameters
         ----------
@@ -178,12 +179,13 @@ def growth_rate(self, z):
             -1
             - self.cosmo.Om(z) / 2
             + self.cosmo.Ode(z)
-            + 5 * self.cosmo.Om(z) / (2 * self.growth_factor(z))
+            + 5 * self.cosmo.Om(z) / (2 * self.growth_factor(z) * (1 + z))
         )
 
     def growth_rate_fn(self, zmin=0):
         """
         Growth rate, dln(d)/dln(a) from Hamilton 2000 eq. 4, as callable.
+        Note that the growth function g in Hamilton 2000 is defined as g=D*(1+z).
 
         Parameters
         ----------
@@ -198,7 +200,10 @@ def growth_rate_fn(self, zmin=0):
         gfn = self.growth_factor_fn(zmin)
 
         return lambda z: (
-            -1 - self.cosmo.Om(z) / 2 + self.cosmo.Ode(z) + 5 * self.cosmo.Om(z) / (2 * gfn(z))
+            -1
+            - self.cosmo.Om(z) / 2
+            + self.cosmo.Ode(z)
+            + 5 * self.cosmo.Om(z) / (2 * gfn(z) * (1 + z))
         )