diff --git a/core/build.gradle.kts b/core/build.gradle.kts
index 150bf8b2b..72cabd856 100644
--- a/core/build.gradle.kts
+++ b/core/build.gradle.kts
@@ -121,7 +121,7 @@ dependencies {
   implementation("com.fasterxml.jackson.core:jackson-annotations:${JACKSON_VERSION}")
   implementation("com.fasterxml.jackson.datatype:jackson-datatype-jdk8:${JACKSON_VERSION}")
   implementation("com.fasterxml.jackson.dataformat:jackson-dataformat-yaml:${JACKSON_VERSION}")
-  implementation("com.google.code.findbugs:jsr305:3.0.2")
+  api("org.jspecify:jspecify:1.0.0")
 
   antlr("org.antlr:antlr4:${ANTLR_VERSION}")
   shadowImplementation("org.antlr:antlr4-runtime:${ANTLR_VERSION}")
diff --git a/core/src/main/java/io/substrait/extension/SimpleExtension.java b/core/src/main/java/io/substrait/extension/SimpleExtension.java
index 9f7d64e6b..517bc8fee 100644
--- a/core/src/main/java/io/substrait/extension/SimpleExtension.java
+++ b/core/src/main/java/io/substrait/extension/SimpleExtension.java
@@ -26,8 +26,8 @@
 import java.util.stream.Collectors;
 import java.util.stream.IntStream;
 import java.util.stream.Stream;
-import javax.annotation.Nullable;
 import org.immutables.value.Value;
+import org.jspecify.annotations.Nullable;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -79,12 +79,10 @@ public interface Argument {
     String toTypeString();
 
     @JsonProperty()
-    @Nullable
-    String name();
+    @Nullable String name();
 
     @JsonProperty()
-    @Nullable
-    String description();
+    @Nullable String description();
 
     boolean required();
   }
diff --git a/isthmus/build.gradle.kts b/isthmus/build.gradle.kts
index 64f9891a4..131f43ee2 100644
--- a/isthmus/build.gradle.kts
+++ b/isthmus/build.gradle.kts
@@ -139,7 +139,6 @@ dependencies {
     exclude("com.google.guava", "guava")
       .because("Brings in Guava for Android, which we don't want (and breaks multimaps).")
   }
-  implementation("com.google.code.findbugs:jsr305:3.0.2")
   implementation("org.immutables:value-annotations:${IMMUTABLES_VERSION}")
   implementation("org.slf4j:slf4j-api:${SLF4J_VERSION}")
   annotationProcessor("org.immutables:value:${IMMUTABLES_VERSION}")
@@ -150,6 +149,7 @@ dependencies {
       )
   }
   testImplementation("com.google.protobuf:protobuf-java:${PROTOBUF_VERSION}")
+  api("org.jspecify:jspecify:1.0.0")
 }
 
 tasks {
diff --git a/isthmus/src/main/java/io/substrait/isthmus/TypeConverter.java b/isthmus/src/main/java/io/substrait/isthmus/TypeConverter.java
index f94c63f49..c621425c8 100644
--- a/isthmus/src/main/java/io/substrait/isthmus/TypeConverter.java
+++ b/isthmus/src/main/java/io/substrait/isthmus/TypeConverter.java
@@ -12,11 +12,11 @@
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
-import javax.annotation.Nullable;
 import org.apache.calcite.rel.type.RelDataType;
 import org.apache.calcite.rel.type.RelDataTypeFactory;
 import org.apache.calcite.sql.type.MapSqlType;
 import org.apache.calcite.sql.type.SqlTypeName;
+import org.jspecify.annotations.Nullable;
 
 public class TypeConverter {
 
diff --git a/isthmus/src/main/java/io/substrait/isthmus/UserTypeMapper.java b/isthmus/src/main/java/io/substrait/isthmus/UserTypeMapper.java
index 3394b05b1..2c4665090 100644
--- a/isthmus/src/main/java/io/substrait/isthmus/UserTypeMapper.java
+++ b/isthmus/src/main/java/io/substrait/isthmus/UserTypeMapper.java
@@ -1,8 +1,8 @@
 package io.substrait.isthmus;
 
 import io.substrait.type.Type;
-import javax.annotation.Nullable;
 import org.apache.calcite.rel.type.RelDataType;
+import org.jspecify.annotations.Nullable;
 
 /** Defines conversion of user-defined types between Substrait and Calcite */
 public interface UserTypeMapper {
@@ -10,13 +10,11 @@ public interface UserTypeMapper {
    * @param relDataType the Calcite {@link RelDataType} type to convert
    * @return the Substrait representation of the input type
    */
-  @Nullable
-  Type toSubstrait(RelDataType relDataType);
+  @Nullable Type toSubstrait(RelDataType relDataType);
 
   /**
    * @param type the Subtrait {@link Type.UserDefined} type to convert
    * @return the Calcite {@link RelDataType} representing the input type
    */
-  @Nullable
-  RelDataType toCalcite(Type.UserDefined type);
+  @Nullable RelDataType toCalcite(Type.UserDefined type);
 }
diff --git a/isthmus/src/main/java/io/substrait/isthmus/calcite/SubstraitOperatorTable.java b/isthmus/src/main/java/io/substrait/isthmus/calcite/SubstraitOperatorTable.java
index c6cc29d6b..b363203e3 100644
--- a/isthmus/src/main/java/io/substrait/isthmus/calcite/SubstraitOperatorTable.java
+++ b/isthmus/src/main/java/io/substrait/isthmus/calcite/SubstraitOperatorTable.java
@@ -15,7 +15,7 @@
 import org.apache.calcite.sql.fun.SqlStdOperatorTable;
 import org.apache.calcite.sql.util.SqlOperatorTables;
 import org.apache.calcite.sql.validate.SqlNameMatcher;
-import org.checkerframework.checker.nullness.qual.Nullable;
+import org.jspecify.annotations.Nullable;
 
 /**
  * Overrides SQL operator lookups to return Substrait specific functions variants (e.g. {@link
diff --git a/isthmus/src/main/java/io/substrait/isthmus/expression/CallConverters.java b/isthmus/src/main/java/io/substrait/isthmus/expression/CallConverters.java
index f030b61da..5dbd88055 100644
--- a/isthmus/src/main/java/io/substrait/isthmus/expression/CallConverters.java
+++ b/isthmus/src/main/java/io/substrait/isthmus/expression/CallConverters.java
@@ -10,12 +10,12 @@
 import java.util.List;
 import java.util.Optional;
 import java.util.function.Function;
-import javax.annotation.Nullable;
 import org.apache.calcite.rex.RexBuilder;
 import org.apache.calcite.rex.RexCall;
 import org.apache.calcite.rex.RexNode;
 import org.apache.calcite.rex.RexUtil;
 import org.apache.calcite.sql.SqlKind;
+import org.jspecify.annotations.Nullable;
 
 public class CallConverters {
 
@@ -146,8 +146,7 @@ public static List<CallConverter> defaults(TypeConverter typeConverter) {
 
   public interface SimpleCallConverter extends CallConverter {
 
-    @Nullable
-    Expression apply(RexCall call, Function<RexNode, Expression> topLevelConverter);
+    @Nullable Expression apply(RexCall call, Function<RexNode, Expression> topLevelConverter);
 
     @Override
     default Optional<Expression> convert(
diff --git a/isthmus/src/test/java/io/substrait/isthmus/CalciteTypeTest.java b/isthmus/src/test/java/io/substrait/isthmus/CalciteTypeTest.java
index 99a6aa79b..1d751e09e 100644
--- a/isthmus/src/test/java/io/substrait/isthmus/CalciteTypeTest.java
+++ b/isthmus/src/test/java/io/substrait/isthmus/CalciteTypeTest.java
@@ -8,9 +8,9 @@
 import io.substrait.type.TypeCreator;
 import java.util.Arrays;
 import java.util.List;
-import javax.annotation.Nullable;
 import org.apache.calcite.rel.type.RelDataType;
 import org.apache.calcite.sql.type.SqlTypeName;
+import org.jspecify.annotations.Nullable;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.ValueSource;
diff --git a/isthmus/src/test/java/io/substrait/isthmus/ComplexSortTest.java b/isthmus/src/test/java/io/substrait/isthmus/ComplexSortTest.java
index 3f7407530..dff92e557 100644
--- a/isthmus/src/test/java/io/substrait/isthmus/ComplexSortTest.java
+++ b/isthmus/src/test/java/io/substrait/isthmus/ComplexSortTest.java
@@ -15,7 +15,7 @@
 import org.apache.calcite.rel.externalize.RelWriterImpl;
 import org.apache.calcite.sql.SqlExplainLevel;
 import org.apache.calcite.util.Pair;
-import org.checkerframework.checker.nullness.qual.Nullable;
+import org.jspecify.annotations.Nullable;
 import org.junit.jupiter.api.Test;
 
 public class ComplexSortTest extends PlanTestBase {
diff --git a/isthmus/src/test/java/io/substrait/isthmus/CustomFunctionTest.java b/isthmus/src/test/java/io/substrait/isthmus/CustomFunctionTest.java
index 4772468ad..de63c38d1 100644
--- a/isthmus/src/test/java/io/substrait/isthmus/CustomFunctionTest.java
+++ b/isthmus/src/test/java/io/substrait/isthmus/CustomFunctionTest.java
@@ -21,7 +21,6 @@
 import io.substrait.type.TypeCreator;
 import java.io.IOException;
 import java.util.List;
-import javax.annotation.Nullable;
 import org.apache.calcite.rel.RelNode;
 import org.apache.calcite.rel.type.RelDataType;
 import org.apache.calcite.rel.type.RelDataTypeFactory;
@@ -34,6 +33,7 @@
 import org.apache.calcite.sql.type.SqlTypeFactoryImpl;
 import org.apache.calcite.sql.type.SqlTypeName;
 import org.apache.calcite.tools.RelBuilder;
+import org.jspecify.annotations.Nullable;
 import org.junit.jupiter.api.Test;
 
 /** Verify that custom functions can convert from Substrait to Calcite and back. */