diff --git a/openmc/capi/core.py b/openmc/capi/core.py
index ad4f77dff..baba0b833 100644
--- a/openmc/capi/core.py
+++ b/openmc/capi/core.py
@@ -230,18 +230,9 @@ def keff():
         Mean k-eigenvalue and standard deviation of the mean
 
     """
-    n = openmc.capi.num_realizations()
-    if n > 3:
-        # Use the combined estimator if there are enough realizations
-        k = (c_double*2)()
-        _dll.openmc_get_keff(k)
-        return tuple(k)
-    else:
-        # Otherwise, return the tracklength estimator
-        mean = c_double.in_dll(_dll, 'keff').value
-        std_dev = c_double.in_dll(_dll, 'keff_std').value \
-                  if n > 1 else np.inf
-        return (mean, std_dev)
+    k = (c_double*2)()
+    _dll.openmc_get_keff(k)
+    return tuple(k)
 
 
 def master():
diff --git a/src/eigenvalue.cpp b/src/eigenvalue.cpp
index 08a4d3f91..0d6aa19b3 100644
--- a/src/eigenvalue.cpp
+++ b/src/eigenvalue.cpp
@@ -29,6 +29,7 @@
 #include <cmath> // for sqrt, abs, pow
 #include <iterator> // for back_inserter
 #include <string>
+#include <limits> //for infinity
 
 namespace openmc {
 
@@ -388,10 +389,15 @@ int openmc_get_keff(double* k_combined)
   k_combined[0] = 0.0;
   k_combined[1] = 0.0;
 
-  // Make sure we have at least four realizations. Notice that at the end,
-  // there is a N-3 term in a denominator.
+  //Special case for n <=3. Notice that at the end,
+  //there is a N-3 term in a denominator.
   if (simulation::n_realizations <= 3) {
-    return -1;
+    k_combined[0] = simulation::keff;
+    k_combined[1] = simulation::keff_std;
+    if (simulation::n_realizations <=1){
+      k_combined[1] = std::numeric_limits<double>::infinity();
+    }
+    return 0;
   }
 
   // Initialize variables