diff --git a/lib/sdam/server_selection.js b/lib/sdam/server_selection.js
index 6286ab5d3a..84da156b11 100644
--- a/lib/sdam/server_selection.js
+++ b/lib/sdam/server_selection.js
@@ -47,7 +47,7 @@ function maxStalenessReducer(readPreference, topologyDescription, servers) {
   }
 
   if (topologyDescription.type === TopologyType.ReplicaSetWithPrimary) {
-    const primary = servers.filter(primaryFilter)[0];
+    const primary = Array.from(topologyDescription.servers.values()).filter(primaryFilter)[0];
     return servers.reduce((result, server) => {
       const stalenessMS =
         server.lastUpdateTime -
@@ -196,50 +196,32 @@ function readPreferenceServerSelector(readPreference) {
       return latencyWindowReducer(topologyDescription, servers.filter(knownFilter));
     }
 
-    if (readPreference.mode === ReadPreference.PRIMARY) {
+    const mode = readPreference.mode;
+    if (mode === ReadPreference.PRIMARY) {
       return servers.filter(primaryFilter);
     }
 
-    if (readPreference.mode === ReadPreference.SECONDARY) {
-      return latencyWindowReducer(
-        topologyDescription,
-        tagSetReducer(
-          readPreference,
-          maxStalenessReducer(readPreference, topologyDescription, servers)
-        )
-      ).filter(secondaryFilter);
-    } else if (readPreference.mode === ReadPreference.NEAREST) {
-      return latencyWindowReducer(
-        topologyDescription,
-        tagSetReducer(
-          readPreference,
-          maxStalenessReducer(readPreference, topologyDescription, servers)
-        )
-      ).filter(nearestFilter);
-    } else if (readPreference.mode === ReadPreference.SECONDARY_PREFERRED) {
-      const result = latencyWindowReducer(
-        topologyDescription,
-        tagSetReducer(
-          readPreference,
-          maxStalenessReducer(readPreference, topologyDescription, servers)
-        )
-      ).filter(secondaryFilter);
-
-      return result.length === 0 ? servers.filter(primaryFilter) : result;
-    } else if (readPreference.mode === ReadPreference.PRIMARY_PREFERRED) {
+    if (mode === ReadPreference.PRIMARY_PREFERRED) {
       const result = servers.filter(primaryFilter);
       if (result.length) {
         return result;
       }
+    }
+
+    const filter = mode === ReadPreference.NEAREST ? nearestFilter : secondaryFilter;
+    const selectedServers = latencyWindowReducer(
+      topologyDescription,
+      tagSetReducer(
+        readPreference,
+        maxStalenessReducer(readPreference, topologyDescription, servers.filter(filter))
+      )
+    );
 
-      return latencyWindowReducer(
-        topologyDescription,
-        tagSetReducer(
-          readPreference,
-          maxStalenessReducer(readPreference, topologyDescription, servers)
-        )
-      ).filter(secondaryFilter);
+    if (mode === ReadPreference.SECONDARY_PREFERRED && selectedServers.length === 0) {
+      return servers.filter(primaryFilter);
     }
+
+    return selectedServers;
   };
 }
 
diff --git a/test/spec/max-staleness/Unknown/SmallMaxStaleness.json b/test/spec/max-staleness/Unknown/SmallMaxStaleness.json
index 73957ab6e8..bf6174b8e4 100644
--- a/test/spec/max-staleness/Unknown/SmallMaxStaleness.json
+++ b/test/spec/max-staleness/Unknown/SmallMaxStaleness.json
@@ -5,7 +5,8 @@
     "servers": [
       {
         "address": "a:27017",
-        "type": "Unknown"
+        "type": "Unknown",
+        "maxWireVersion": 5
       }
     ]
   },
diff --git a/test/spec/max-staleness/Unknown/SmallMaxStaleness.yml b/test/spec/max-staleness/Unknown/SmallMaxStaleness.yml
index 7daaa1fb4a..3a39615ac0 100644
--- a/test/spec/max-staleness/Unknown/SmallMaxStaleness.yml
+++ b/test/spec/max-staleness/Unknown/SmallMaxStaleness.yml
@@ -7,6 +7,7 @@ topology_description:
   - &1
     address: a:27017
     type: Unknown
+    maxWireVersion: 5
 read_preference:
   mode: Nearest
   maxStalenessSeconds: 1
diff --git a/test/spec/server-selection/server_selection/ReplicaSetWithPrimary/read/Nearest.json b/test/spec/server-selection/server_selection/ReplicaSetWithPrimary/read/Nearest.json
index cfe4965938..45b3725585 100644
--- a/test/spec/server-selection/server_selection/ReplicaSetWithPrimary/read/Nearest.json
+++ b/test/spec/server-selection/server_selection/ReplicaSetWithPrimary/read/Nearest.json
@@ -4,7 +4,7 @@
     "servers": [
       {
         "address": "b:27017",
-        "avg_rtt_ms": 5,
+        "avg_rtt_ms": 21,
         "type": "RSSecondary",
         "tags": {
           "data_center": "nyc"
@@ -20,11 +20,19 @@
       },
       {
         "address": "a:27017",
-        "avg_rtt_ms": 26,
+        "avg_rtt_ms": 37,
         "type": "RSPrimary",
         "tags": {
           "data_center": "nyc"
         }
+      },
+      {
+        "address": "d:27017",
+        "avg_rtt_ms": 5,
+        "type": "RSOther",
+        "tags": {
+          "data_center": "nyc"
+        }
       }
     ]
   },
@@ -40,7 +48,7 @@
   "suitable_servers": [
     {
       "address": "b:27017",
-      "avg_rtt_ms": 5,
+      "avg_rtt_ms": 21,
       "type": "RSSecondary",
       "tags": {
         "data_center": "nyc"
@@ -48,7 +56,7 @@
     },
     {
       "address": "a:27017",
-      "avg_rtt_ms": 26,
+      "avg_rtt_ms": 37,
       "type": "RSPrimary",
       "tags": {
         "data_center": "nyc"
@@ -66,7 +74,7 @@
   "in_latency_window": [
     {
       "address": "b:27017",
-      "avg_rtt_ms": 5,
+      "avg_rtt_ms": 21,
       "type": "RSSecondary",
       "tags": {
         "data_center": "nyc"
diff --git a/test/spec/server-selection/server_selection/ReplicaSetWithPrimary/read/Nearest.yml b/test/spec/server-selection/server_selection/ReplicaSetWithPrimary/read/Nearest.yml
index 5e8e0499d2..1ffb3df32c 100644
--- a/test/spec/server-selection/server_selection/ReplicaSetWithPrimary/read/Nearest.yml
+++ b/test/spec/server-selection/server_selection/ReplicaSetWithPrimary/read/Nearest.yml
@@ -3,7 +3,7 @@ topology_description:
   servers:
   - &1
     address: b:27017
-    avg_rtt_ms: 5
+    avg_rtt_ms: 21
     type: RSSecondary
     tags:
       data_center: nyc
@@ -15,10 +15,15 @@ topology_description:
       data_center: nyc
   - &2
     address: a:27017
-    avg_rtt_ms: 26
+    avg_rtt_ms: 37
     type: RSPrimary
     tags:
       data_center: nyc
+  - address: d:27017
+    avg_rtt_ms: 5
+    type: RSOther
+    tags:
+      data_center: nyc
 operation: read
 read_preference:
   mode: Nearest
diff --git a/test/spec/server-selection/server_selection/ReplicaSetWithPrimary/read/Secondary.json b/test/spec/server-selection/server_selection/ReplicaSetWithPrimary/read/Secondary.json
index 23864a278c..a2e35a769c 100644
--- a/test/spec/server-selection/server_selection/ReplicaSetWithPrimary/read/Secondary.json
+++ b/test/spec/server-selection/server_selection/ReplicaSetWithPrimary/read/Secondary.json
@@ -4,7 +4,7 @@
     "servers": [
       {
         "address": "b:27017",
-        "avg_rtt_ms": 5,
+        "avg_rtt_ms": 21,
         "type": "RSSecondary",
         "tags": {
           "data_center": "nyc"
@@ -20,7 +20,7 @@
       },
       {
         "address": "a:27017",
-        "avg_rtt_ms": 26,
+        "avg_rtt_ms": 5,
         "type": "RSPrimary",
         "tags": {
           "data_center": "nyc"
@@ -40,7 +40,7 @@
   "suitable_servers": [
     {
       "address": "b:27017",
-      "avg_rtt_ms": 5,
+      "avg_rtt_ms": 21,
       "type": "RSSecondary",
       "tags": {
         "data_center": "nyc"
@@ -58,7 +58,7 @@
   "in_latency_window": [
     {
       "address": "b:27017",
-      "avg_rtt_ms": 5,
+      "avg_rtt_ms": 21,
       "type": "RSSecondary",
       "tags": {
         "data_center": "nyc"
diff --git a/test/spec/server-selection/server_selection/ReplicaSetWithPrimary/read/Secondary.yml b/test/spec/server-selection/server_selection/ReplicaSetWithPrimary/read/Secondary.yml
index 85afe014a1..031643e814 100644
--- a/test/spec/server-selection/server_selection/ReplicaSetWithPrimary/read/Secondary.yml
+++ b/test/spec/server-selection/server_selection/ReplicaSetWithPrimary/read/Secondary.yml
@@ -3,18 +3,18 @@ topology_description:
   servers:
   - &1
     address: b:27017
-    avg_rtt_ms: 5
+    avg_rtt_ms: 21 # outside the latency window if primary is considered
     type: RSSecondary
     tags:
       data_center: nyc
   - &2
     address: c:27017
-    avg_rtt_ms: 100
+    avg_rtt_ms: 100 # outside the latency window if both secondaries are considered
     type: RSSecondary
     tags:
       data_center: nyc
   - address: a:27017
-    avg_rtt_ms: 26
+    avg_rtt_ms: 5
     type: RSPrimary
     tags:
       data_center: nyc