diff --git a/src/mlpack/methods/approx_kfn/approx_kfn_main.cpp b/src/mlpack/methods/approx_kfn/approx_kfn_main.cpp
index f362ae7c00..9adce050e6 100644
--- a/src/mlpack/methods/approx_kfn/approx_kfn_main.cpp
+++ b/src/mlpack/methods/approx_kfn/approx_kfn_main.cpp
@@ -189,6 +189,16 @@ static void mlpackMain()
         "the reference set must be passed");
   }
 
+  if (CLI::HasParam("k") && CLI::HasParam("reference") &&
+      ((size_t) CLI::GetParam<int>("k")) >
+          CLI::GetParam<arma::mat>("reference").n_cols)
+  {
+    Log::Fatal << "Number of neighbors to search for ("
+        << CLI::GetParam<int>("k") << ") must be less than the number of "
+        << "reference points ("
+        << CLI::GetParam<arma::mat>("reference").n_cols << ")." << std::endl;
+  }
+
   // Do the building of a model, if necessary.
   ApproxKFNModel* m;
   arma::mat referenceSet; // This may be used at query time.
@@ -264,16 +274,23 @@ static void mlpackMain()
       if (CLI::HasParam("exact_distances"))
       {
         // Check the exact distances matrix has the right dimensions.
-        RequireParamValue<arma::mat>("exact_distances",
-          [&](const arma::mat& exactDists){ return (exactDists.n_rows == k); },
-          true, "the number of rows in exact distances matrix must be equal to "
-          "k.");
-        RequireParamValue<arma::mat>("exact_distances",
-          [&](const arma::mat& exactDists){ return (exactDists.n_cols ==
-          referenceSet.n_cols); }, true, "the number of columns in exact "
-          "distances matrix must be equal to the number of columns in "
-          "reference set.");
         exactDistances = std::move(CLI::GetParam<arma::mat>("exact_distances"));
+
+        if (exactDistances.n_rows != k)
+        {
+          delete m;
+          Log::Fatal << "The number of rows in the exact distances matrix ("
+              << exactDistances.n_rows << " must be equal to k (" << k << ")."
+              << std::endl;
+        }
+        else if (exactDistances.n_cols != referenceSet.n_cols)
+        {
+          delete m;
+          Log::Fatal << "The number of columns in the exact distances matrix ("
+              << exactDistances.n_cols << ") must be equal to the number of "
+              << "columns in the reference set (" << referenceSet.n_cols << ")."
+              << std::endl;
+        }
       }
       else
       {
diff --git a/src/mlpack/tests/main_tests/approx_kfn_test.cpp b/src/mlpack/tests/main_tests/approx_kfn_test.cpp
index c60874c73c..3633df8c4e 100644
--- a/src/mlpack/tests/main_tests/approx_kfn_test.cpp
+++ b/src/mlpack/tests/main_tests/approx_kfn_test.cpp
@@ -73,7 +73,7 @@ BOOST_AUTO_TEST_CASE(ApproxKFNInvalidKTest)
   SetInputParam("k", (int) 81); // Invalid.
 
   Log::Fatal.ignoreInput = true;
-  BOOST_REQUIRE_THROW(mlpackMain(), std::invalid_argument);
+  BOOST_REQUIRE_THROW(mlpackMain(), std::runtime_error);
   Log::Fatal.ignoreInput = false;
 }