diff --git a/openmc/capi/core.py b/openmc/capi/core.py
index ad4f77dfff..baba0b833f 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 08a4d3f91c..04fdabab1b 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,
+  // 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
diff --git a/tests/regression_tests/filter_distribcell/case-1/results_true.dat b/tests/regression_tests/filter_distribcell/case-1/results_true.dat
index 2d9835b1ab..80036a7c47 100644
--- a/tests/regression_tests/filter_distribcell/case-1/results_true.dat
+++ b/tests/regression_tests/filter_distribcell/case-1/results_true.dat
@@ -1,5 +1,5 @@
 k-combined:
-0.000000E+00 0.000000E+00
+5.497140E-02          INF
 tally 1:
 1.548980E-02
 2.399339E-04
diff --git a/tests/regression_tests/filter_distribcell/case-2/results_true.dat b/tests/regression_tests/filter_distribcell/case-2/results_true.dat
index 57e40f4962..bbf38b3d1c 100644
--- a/tests/regression_tests/filter_distribcell/case-2/results_true.dat
+++ b/tests/regression_tests/filter_distribcell/case-2/results_true.dat
@@ -1,5 +1,5 @@
 k-combined:
-0.000000E+00 0.000000E+00
+2.149726E-02          INF
 tally 1:
 7.588170E-03
 5.758032E-05
diff --git a/tests/regression_tests/filter_distribcell/case-3/results_true.dat b/tests/regression_tests/filter_distribcell/case-3/results_true.dat
index 0a4dd9dc76..be197b5e9f 100644
--- a/tests/regression_tests/filter_distribcell/case-3/results_true.dat
+++ b/tests/regression_tests/filter_distribcell/case-3/results_true.dat
@@ -1 +1 @@
-11755ecac8355b5e79384f5d72974e618b6f95500c0a5718c01bb340c5d1c8ceafc33de65b9e94b7e9d78f16ec209f8a0fdf6a531eab5430657688d0125db7ef
\ No newline at end of file
+2ee0162762999f71ad2178936509fd9e054928023a9e0e90c078cede3ecf6583267069486adf15f1b02188333d1bfe1fc41b341bc00aab53feddd1395441f1f8
\ No newline at end of file
diff --git a/tests/regression_tests/filter_distribcell/case-4/results_true.dat b/tests/regression_tests/filter_distribcell/case-4/results_true.dat
index 078e74bed1..43a837e983 100644
--- a/tests/regression_tests/filter_distribcell/case-4/results_true.dat
+++ b/tests/regression_tests/filter_distribcell/case-4/results_true.dat
@@ -1,5 +1,5 @@
 k-combined:
-0.000000E+00 0.000000E+00
+1.121246E-01          INF
 tally 1:
 2.265319E-02
 5.131668E-04
diff --git a/tests/regression_tests/sourcepoint_batch/results_true.dat b/tests/regression_tests/sourcepoint_batch/results_true.dat
index 8b8dd98f2b..a9843df530 100644
--- a/tests/regression_tests/sourcepoint_batch/results_true.dat
+++ b/tests/regression_tests/sourcepoint_batch/results_true.dat
@@ -1,3 +1,3 @@
 k-combined:
-0.000000E+00 0.000000E+00
+2.976389E-01 3.770725E-03
 1.892327E+00 -3.385257E+00 6.702632E-01