diff --git a/release-notes/VERSION-2.x b/release-notes/VERSION-2.x
index d76b28b48f..494d47c4f2 100644
--- a/release-notes/VERSION-2.x
+++ b/release-notes/VERSION-2.x
@@ -41,6 +41,9 @@ Project: jackson-databind
 
 #2486: Builder Deserialization with JsonCreator Value vs Array
  (reported by Ville K)
+#2755: `StdSubtypeResolver` is not thread safe (possibly due to copy
+  not being made with `ObjectMapper.copy()`)
+ (reported by tjwilson90@github)
 
 2.11.0 (26-Apr-2020)
 
diff --git a/src/main/java/com/fasterxml/jackson/databind/deser/std/DateDeserializers.java b/src/main/java/com/fasterxml/jackson/databind/deser/std/DateDeserializers.java
index 3d59d2122e..6635169544 100644
--- a/src/main/java/com/fasterxml/jackson/databind/deser/std/DateDeserializers.java
+++ b/src/main/java/com/fasterxml/jackson/databind/deser/std/DateDeserializers.java
@@ -14,7 +14,6 @@
 import com.fasterxml.jackson.databind.*;
 import com.fasterxml.jackson.databind.annotation.JacksonStdImpl;
 import com.fasterxml.jackson.databind.cfg.CoercionAction;
-import com.fasterxml.jackson.databind.cfg.CoercionInputShape;
 import com.fasterxml.jackson.databind.deser.ContextualDeserializer;
 import com.fasterxml.jackson.databind.type.LogicalType;
 import com.fasterxml.jackson.databind.util.ClassUtil;
diff --git a/src/test/java/com/fasterxml/jackson/databind/objectid/ObjectId687Test.java b/src/test/java/com/fasterxml/jackson/databind/objectid/ObjectId687Test.java
index 972a5fa8f9..91eda5e44b 100644
--- a/src/test/java/com/fasterxml/jackson/databind/objectid/ObjectId687Test.java
+++ b/src/test/java/com/fasterxml/jackson/databind/objectid/ObjectId687Test.java
@@ -63,7 +63,7 @@ static class EnclosingForRefWithNoCreator {
     /*****************************************************
      */
 
-    private final ObjectMapper MAPPER = objectMapper();
+    private final ObjectMapper MAPPER = newJsonMapper();
 
     // for [databind#687]
     public void testSerializeDeserializeWithCreator() throws IOException {
diff --git a/src/test/java/com/fasterxml/jackson/databind/objectid/ObjectId825BTest.java b/src/test/java/com/fasterxml/jackson/databind/objectid/ObjectId825BTest.java
index 1812db6b2e..bfb3251d84 100644
--- a/src/test/java/com/fasterxml/jackson/databind/objectid/ObjectId825BTest.java
+++ b/src/test/java/com/fasterxml/jackson/databind/objectid/ObjectId825BTest.java
@@ -136,10 +136,15 @@ static class V extends AbstractData {
         private static final long serialVersionUID = 1L;
     }    
 
+    /*
+    /*****************************************************
+    /* Test methods
+    /*****************************************************
+     */
+
     public void testFull825() throws Exception
     {
         final ObjectMapper mapper = jsonMapperBuilder()
-                .enable(DeserializationFeature.ACCEPT_EMPTY_STRING_AS_NULL_OBJECT)
                 .activateDefaultTyping(NoCheckSubTypeValidator.instance,
                         DefaultTyping.OBJECT_AND_NON_CONCRETE)
                 .build();
diff --git a/src/test/java/com/fasterxml/jackson/databind/ser/TestArraySerialization.java b/src/test/java/com/fasterxml/jackson/databind/ser/TestArraySerialization.java
index 74740d492f..05c84bf97d 100644
--- a/src/test/java/com/fasterxml/jackson/databind/ser/TestArraySerialization.java
+++ b/src/test/java/com/fasterxml/jackson/databind/ser/TestArraySerialization.java
@@ -6,7 +6,7 @@
 public class TestArraySerialization
     extends BaseMapTest
 {
-    private final ObjectMapper MAPPER = newJsonMapper();
+    private final ObjectMapper MAPPER = sharedMapper();
     
     public void testLongStringArray() throws Exception
     {